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Henry has been a longtime colleague of mine
working in the early days of Apollo and Shuttle.
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He is an old country boy but he has created
more innovative designs on technical problems
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than anybody I know.
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And we will try to bring some of those out
because he has really created some very innovative
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solutions to technical problems.
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And I am going to set Henry up a little bit
so let me set the stage for you a little bit.
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I was manager of the Space Shuttle Orbiter,
and the engineers came to me and said, Aaron,
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the waste management system on the Shuttle
is not working very well.
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Now, the waste management system, in simple
terms, is the toilet.
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They said the toilet is not working very well,
and we really need to go off and design a
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new toilet.
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I thought for a moment, well, that's probably
a pretty important thing to do, so we did.
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Well, it turns out the original contract,
and I am quoting a little bit from memory,
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was about $10 million.
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Now, $10 million for a toilet when you can
go down to any place and get a toilet for
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a couple hundred dollars is a pretty high
number.
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But that wasn't the worst of it.
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The worst of it, about six months later they
came to me and said, Aaron, guess what?
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It's not $10 million.
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It's $20 million.
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Congress got wind of this and wanted me to
come up and testify.
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And you can see what kind of fun they are
going to have.
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Waste management, they're really going to
have fun with this subject.
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And you may know some people in congress,
but the name was Mr.
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Sensenbrenner from Wisconsin.
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I remember very clearly.
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He is still in congress now.
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He was head of the Science Committee, and
that is who we had to go testify for.
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Well, there was a reporter for The Washington
Post.
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Her name was Kathy Sawyer.
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Now, Kathy was the science reporter for The
Washington Post.
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Very, very good.
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Kathy was very smart, very fair, but she really
bore in on things.
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Kathy got wind of this so she wanted to publish
an article on it.
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She called me and said would you please talk
to me about the waste management system?
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I said, boy, she is going to get me in trouble.
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I said, I will tell you what, I've got somebody
that could really tell you about the waste
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management system, and I will have Henry Pohl
call you.
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I talked to Henry about it.
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Now, that is going to be Henry's introduction
to this class of what he told Kathy Sawyer
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because it is a classic.
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Henry, it is all yours.
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Aaron almost forgot
about Kathy Sawyer.
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Kathy called me up and said can you explain
to me how I might explain to my neighbor's
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14 year old daughter why NASA has spent $10
million building a toilet?
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And I said I will try.
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And I thought for a little bit on how am I
going to start out on this?
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I said, you know, if you take the commode
that you've got in your bathroom and you bolt
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it upside down on the ceiling, now try using
it.
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[LAUGHTER] I said that is really a little
better situation than we have on the Orbiter
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because at least we know which way the gravity
field is on that.
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In orbit you don't know.
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Most of the time you don't have any, but it
might be to the right or left or up or down.
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You know, that was the only reporter that
I ever talked to it that put everything down
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verbatim of what I said, the questions she
asked and what I said and printed that article
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in the newspaper.
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But that kind of sets a stage for operating
in the absence of gravity.
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I explained to her that the Space Shuttle
volume that the people had to live in is about
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the same volume as you have in a modern bathroom.
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If you look at a bathroom with a shower and
a room just outside with a sink and everything,
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we have just about that same volume in the
Shuttle.
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Now, you seal that all up, you've got a certain
amount of air that you can use in there and
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you only have the air to replace gravity.
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You've got to have a flow of air to direct
whatever you want to direct in a certain direction.
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You use that air.
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You run it through.
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You've got to deodorize it.
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You've got to clean it.
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You've got to run it back into the cabin almost
instantly.
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Otherwise, you pull the vacuum in the cabin.
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And so whenever you start putting all of that
equipment in there and all that stuff in there
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on something that has never been done before,
$10 million or $20 million is kind of cheap
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when you get right down to it.
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You look at the number of people that that
will hire for a year working on it is cheap.
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But to try to get that message across is not
easy.
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Go ahead and give me my first slide.
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Let me just tell you another one since Aaron
got me off on a tangent here.
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The Chicago Tribune called me one day when
we had a problem on Shuttle, and she was badmouthing
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the Shuttle.
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And all she wanted to do was get a comment
out of me that I agreed with something that
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she said since she could quote it.
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And I said I don't agree with you.
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I said you know that Orbiter is really a pretty
good vehicle when you look at what it has
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to do.
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I said you realize when it's in orbit it is
going eight times faster than a bullet when
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it leaves the muzzle of a .30-06?
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Silence on the other end.
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What's a .30-06?
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Well, I knew that wasn't a good example.
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[LAUGHTER] But I told her that is a military
rifle that was used in the Second World War.
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And I used to fire that thing in the desert.
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And I could pull the trigger and see that
bullet hit the ground out of that 300 yards
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almost instantly.
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Now, that shuttle is going eight times faster
than that.
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And I could see the headlines in the Chicago
Tribune, the shuttle flies eight times faster
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than a bullet.
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Long silence.
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She said maybe I ought to find something else
to write about.
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I said why?
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She said I don't think I have a story here.
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Well, it wasn't a story because it wasn't
negative.
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Kathy Sawyer was the only time I ever got
a good story from the press.
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I want you all to feel free to ask questions.
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I'm here more to talk about what you're interested
in talking about than my thoughts, so feel
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free to ask questions any time.
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I would like to talk about a half an hour.
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Somebody is going to have to tell me when
a half an hour is up.
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And then I would like to have some time for
some questions.
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My first involvement in the Space Shuttle
was Max Faget kind of came up with this idea
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of a winged vehicle going into space.
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And we kicked it around for a while.
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And he formed a little committee, very small,
about 20 people as I recall.
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Put the people in a room.
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He wanted to keep it quiet.
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He wanted to keep it secret until he got enough
data so that he could know whether it was
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feasible or not.
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Well, they wanted me to send the best engineer
I had over there.
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And he appointed a guy by the name of Jim
Chamberlain to head up that group.
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I sent a guy over there.
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They closed the doors, had a guard in front
of the doors so nobody could come in, no information
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could get out.
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On the third day, Jim Chamberlain called me
up and said I need to have a talk with my
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engineer.
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I said why?
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He said he balked.
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I said what do you mean he balked?
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He says, Henry, you know what an old mule
does when they balk, don't you?
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I said, yeah, they won't go.
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He said, well, that's your Mr.
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Kindrick, he won't go.
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I called up my engineer and said what's going
on over there, girl?
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He said, oh, they don't know what they want.
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He said they gave me some requirements.
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I designed them an RCS system for it.
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They gave me another set of requirements.
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I designed another RCS system.
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They gave me some different requirements.
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I designed them a different RCS system.
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And then they came out with another set of
requirements.
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I'm just going to wait until they decide what
they want and then I'll design them an RCS
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system for it.
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Well, what he didn't understand was that's
the way you go about setting the requirements.
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You get a small group of people together.
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You set down a set of requirements.
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You try to put a vehicle together and see
where it punches out.
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Usually weight, CG, something.
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So you change the requirements up a little
bit and you design another system.
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You do that very quickly and you look at where
that one punches out.
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And then you change your requirements again
and you look at those requirements and where
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it punched out.
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The first requirements, where it punched out.
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You change the requirements a little bit and
see where it punches out.
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Very, very quickly you run through many configurations.
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That got the Shuttle started.
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After it got started we kept changing the
requirements as we went through the program.
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I would suggest that you understand your requirements
very, very clearly, and the impact of your
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requirements very clearly.
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Things like fail op fail safe, or fail safe
fail safe fail op are very, very good buzz
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words.
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But unless you really understand the impact
of those, they can actually make a system
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less safe.
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I can make a very good case that a two engine
airplane is safer than a four engine airplane
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simply by the way that you set your requirements.
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FAA has a requirement that an airplane has
to take off with one engine out.
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If you've got a two engine airplane then most
of the time you've got 100% more power than
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you need.
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If you have a four engine airplane you only
have 25% more power than you need.
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Most airplane crashes are caused from lack
of power at the right time.
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If you've got the power when you need it then
you can get out of most bad situations.
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Our original requirements on the Shuttle,
after we got that started, was to keep the
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operations cost low.
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We wanted to keep the maintenance cost and
the operations cost low.
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We initially were looking at oxygen/hydrogen
systems.
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In fact, all of the early orbiters had the
hydrogen/oxygen onboard.
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In place of their payload, we had hydrogen
tanks and oxygen tanks in there and carried
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the hydrogen/oxygen onboard.
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And we actually looked at using the hydrogen
out of those tanks.
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You get it free to power the OMS and the RCS.
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And we looked at all kinds of ways of getting
the pressure up high enough to be able to
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use the residuals to power the vehicle.
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One of the students asked the question the
other day and we didn't give a very good answer
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that we did at one time look at putting the
hydrogen in the payload bay of the Shuttle.
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All of the very early configurations of the
Shuttle had the hydrogen and the oxygen in
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the Shuttle in place of payload bay.
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That was the very early configuration.
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Later on, as DOD got involved and other people
wanted big spaces and carrying greyhound buses
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up there and things like that we had to use
that space and that's when we came up with
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the external tank.
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And that's when we came up with a side-by-side
configuration on it.
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That's the way I recall it.
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But we looked at oxygen/hydrogen.
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Then we went to methane because we were looking
at bulk densities so that we had smaller tanks,
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smaller volumes.
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Then we looked at oxygen/alcohol.
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And I really thought we had a good system
with oxygen/alcohol.
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I had a lot of confidence in that system.
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We used it on Redstone.
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My first job was working on Redstone.
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I really liked alcohol.
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I thought we had developed a good ignition
system for the RCS so we didn't have to worry
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about the thousand starts.
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But obviously that was going to cost us money
and cost a lot of development money.
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And, as time went on, we changed from having
low operational cost to low development cost.
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And when we went to low development cost then
we went to bipropellant on the OMS and initially
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to monopropellant on the RCS.
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When I say bipropellant, what I mean are storables,
monomethyl hydrazine and nitrogen tetroxide.
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Both are storable propellants.
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They are self-igniting so you don't have to
have an ignition system for it.
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That simplifies the design a whole lot.
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We had a lot of experience with those propellants
on Titan II, on Agena and on Apollo, all of
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the Apollo stages used either aerozine 50
and nitrogen tetroxide or monomethyl hydrogen.
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So, we went to that.
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On the RCS, we initially went to hydrazine
as a monopropellant because it was the simplest
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system, the cheapest system, but very quickly
the weight got out of hand and we had to go
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to something that had a little bit more performance
than a hydrazine because all of that weight
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was in the backend of the vehicle.
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And the backend of the vehicle was getting
too heavy.
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If you only remember two things out of this
exercise and what I have to say today, two
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things I want you to remember is that it is
just not natural to think in terms of the
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absence of gravity and it is not natural to
think in terms of the absence of pressure.
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When you think about it, you live in it around
here on the ground, it is so natural that
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it's hard to think in terms of designing systems
and the impact that the absence of gravity
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has or the absence of pressure has on the
design of the systems.
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The other thing I would like for you to remember
is that there is no substitute for a good
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well thought out test program.
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00:17:20,380 --> 00:17:27,380
Let me give you the OMS as an example.
227
00:17:29,840 --> 00:17:36,770
We did not have a vibration test program on
the propulsion systems, on the OMS or the
228
00:17:36,770 --> 00:17:42,080
RCS in the program because, by that time,
we had good structural programs, we could
229
00:17:42,080 --> 00:17:49,080
analyze the effect of vibration and stress
on the vehicle.
230
00:17:49,100 --> 00:17:56,100
But we had a good propulsion test program
and we built an OMS pod, just like the ones
231
00:17:59,480 --> 00:18:01,710
we had on the vehicle for qualification.
232
00:18:01,710 --> 00:18:05,730
And when we got through with all the propulsion
tests on it, and we went through that program
233
00:18:05,730 --> 00:18:10,960
in a breeze, we had no problems at all with
it, so we finished it early.
234
00:18:10,960 --> 00:18:17,960
We took that pod down to JSC, we put it in
a vibro-acoustic facility, and while we were
235
00:18:20,080 --> 00:18:27,080
running the QVVT the low level vibration test
on that pod just to get the response of how
236
00:18:28,539 --> 00:18:35,200
things responded to everything, the helium
bottle fell out.
237
00:18:35,200 --> 00:18:40,570
Five minutes after that helium bottle fell
out every structural guy in the world could
238
00:18:40,570 --> 00:18:47,000
tell you it should have fell out, it would
fall out, but nobody thought about it in advance.
239
00:18:47,000 --> 00:18:51,020
What happened, we had taken a high pressure
helium line coming out of the bottom of the
240
00:18:51,020 --> 00:18:56,730
tank and going five feet or eight feet over
to the structure and bolting it to the structure
241
00:18:56,730 --> 00:18:58,520
over there.
242
00:18:58,520 --> 00:19:04,559
Now, when you started shaking it, that was
acting as a torquing element on that tank
243
00:19:04,559 --> 00:19:07,830
and torquing that tank this way.
244
00:19:07,830 --> 00:19:12,760
And the struts they had coming down holding
the tank, it was fatiguing where they were
245
00:19:12,760 --> 00:19:13,960
put onto the tank.
246
00:19:13,960 --> 00:19:19,380
It fatigued them right in there and broke
them off very quick, but we didn't pick it
247
00:19:19,380 --> 00:19:25,520
up.
248
00:19:25,520 --> 00:19:30,370
The OMS was very, very straightforward from
a development standpoint.
249
00:19:30,370 --> 00:19:34,539
We came out with a platelet injector that
gave us very good combustion.
250
00:19:34,539 --> 00:19:36,690
You have to explain what a platelet injector
is.
251
00:19:36,690 --> 00:19:37,250
OK.
252
00:19:37,250 --> 00:19:44,250
A platelet injector is one where we used photographic
techniques to etch holes in the injector.
253
00:19:46,630 --> 00:19:49,490
You could get a very, very fine pattern.
254
00:19:49,490 --> 00:19:56,270
You made it in very thin sheets and you coated
the sheet with a coating where you could put
255
00:19:56,270 --> 00:19:58,690
them in a press and heat them and glue them
together.
256
00:19:58,690 --> 00:20:05,690
You came up with an injector design that was
made out of many, many thousands of very thin
257
00:20:07,240 --> 00:20:11,559
plates that set up the manifolding on it.
258
00:20:11,559 --> 00:20:15,090
Normal injectors you have to do a lot of very
integrated drilling.
259
00:20:15,090 --> 00:20:19,240
Normal injectors, you drill out a manifold
in the back, and then you take the face plate
260
00:20:19,240 --> 00:20:22,179
and you have to drill holes in it.
261
00:20:22,179 --> 00:20:26,659
And the problem we get into when you start
doing that is with these very small drills
262
00:20:26,659 --> 00:20:29,429
they tend to walk or bend.
263
00:20:29,429 --> 00:20:31,490
And you don't get a straight hole.
264
00:20:31,490 --> 00:20:33,780
You don't get a good spray pattern.
265
00:20:33,780 --> 00:20:39,380
With a platelet injector we could get a very
close match.
266
00:20:39,380 --> 00:20:45,419
We could just kind of dribble a field in there
and oxidizer in there where it always matched
267
00:20:45,419 --> 00:20:46,270
real well.
268
00:20:46,270 --> 00:20:49,159
We got very high performance out of it.
269
00:20:49,159 --> 00:20:56,159
We're talking about the injector up here where
you have the fuel and oxygen, and then you
270
00:20:56,440 --> 00:21:02,230
have to have a whole bunch of holes in a pattern
such that the fuel and the oxidizer are properly
271
00:21:02,230 --> 00:21:04,450
mixed when they ignite inside.
272
00:21:04,450 --> 00:21:11,450
You need to get the oxidizer to impinge on
a fuel very precisely so that with an aero-storable
273
00:21:13,700 --> 00:21:20,480
propellant, a hypergolic propellant as we
call it, that is self-igniting.
274
00:21:20,480 --> 00:21:27,059
And basically what you have is when the two
fuels come together it is like having a very
275
00:21:27,059 --> 00:21:29,960
strong acid and a very strong base coming
together.
276
00:21:29,960 --> 00:21:34,520
The first reaction that you get is a heating
reaction.
277
00:21:34,520 --> 00:21:39,600
That chemical reaction that you get will take
the propellant temperature up to 800, 1000,
278
00:21:39,600 --> 00:21:40,770
1200 degrees.
279
00:21:40,770 --> 00:21:45,780
Anyway, it gets it up to the combustion temperature
and then you start the combustion process.
280
00:21:45,780 --> 00:21:48,360
So you don't have to use any other ignition
source.
281
00:21:48,360 --> 00:21:52,950
All you do is bring those two propellants
together and you get that chemical reaction
282
00:21:52,950 --> 00:21:59,950
that provides the energy, the heat to heat
the propellant to the combustion temperature.
283
00:22:00,539 --> 00:22:04,159
Like all high performance rocket engines,
we had a stability problem with the OMS.
284
00:22:04,159 --> 00:22:07,409
And we had to put big acoustic cavities.
285
00:22:07,409 --> 00:22:14,409
38% of the injector on the OMS was cavities
designed and sized to damp out the stability,
286
00:22:19,710 --> 00:22:21,860
so we had a very good stable engine.
287
00:22:21,860 --> 00:22:27,620
The RCS, on the other hand, is a totally different
design.
288
00:22:27,620 --> 00:22:34,620
Now, we put the propellant tanks on the RCS
up in front of the OMS tanks for aerodynamic
289
00:22:37,159 --> 00:22:37,600
purposes.
290
00:22:37,600 --> 00:22:41,429
That gave us a 30 foot propellant line down
to the RCS.
291
00:22:41,429 --> 00:22:48,429
Then we would manifold three, four, five engines
on the end of that pipe that is pulsing in
292
00:22:49,780 --> 00:22:53,289
and out of phase or steady state.
293
00:22:53,289 --> 00:22:56,860
Some of them were running at 40 millisecond
or 80 millisecond pulses.
294
00:22:56,860 --> 00:23:00,740
Some of them might be running at four times
that on a pulse width.
295
00:23:00,740 --> 00:23:02,620
And some of them may be running at steady
state.
296
00:23:02,620 --> 00:23:09,350
Anyway, the dynamics, the pressure in that
line that the engine sees varies somewhere
297
00:23:09,350 --> 00:23:15,080
between vapor pressure and about 1000 psi.
298
00:23:15,080 --> 00:23:22,080
And, since one propellant is 1.6 times the
density of the other propellant, when that
299
00:23:23,220 --> 00:23:27,070
valve opens down there, that pressure wave
has got to go back up to the tank and come
300
00:23:27,070 --> 00:23:34,070
back down to the injector before you get basically
any flow out of it.
301
00:23:34,860 --> 00:23:39,049
Just the compressibility that you have in
the pipe will come out.
302
00:23:39,049 --> 00:23:41,380
The pressure essentially drops to vapor pressure.
303
00:23:41,380 --> 00:23:44,080
And we use helium to pressurize those tanks.
304
00:23:44,080 --> 00:23:48,429
When we use helium to pressurize those tanks,
the helium is dissolved in the propellant.
305
00:23:48,429 --> 00:23:52,539
When it gets down to the engine it comes out
as solution.
306
00:23:52,539 --> 00:23:59,539
The engine has to be able to stay together
at any mixture ratio and almost any pressure.
307
00:24:01,870 --> 00:24:08,380
And you are looking at hundreds of thousands
of starts over the life of one of those programs
308
00:24:08,380 --> 00:24:10,580
on one of those engines.
309
00:24:10,580 --> 00:24:14,659
And we talk about pulse width.
310
00:24:14,659 --> 00:24:21,659
Pulse width is the minimum ohm time that you
can have on a rocket engine.
311
00:24:21,669 --> 00:24:28,020
Now, there is a volume between the face of
the valve and the face of the injector that
312
00:24:28,020 --> 00:24:32,370
we call dribble volume.
313
00:24:32,370 --> 00:24:37,730
The larger that volume is the larger the pulse
width you need on it.
314
00:24:37,730 --> 00:24:44,730
You would like to have the seat of the valve
to be the face of the injector so you have
315
00:24:45,250 --> 00:24:46,980
zero dribble volume in there.
316
00:24:46,980 --> 00:24:52,520
That way you would get closer to a square
wave pulse.
317
00:24:52,520 --> 00:24:59,520
And your friends in Guidance Control, they
always want to square away pulse.
318
00:24:59,980 --> 00:25:06,789
And they want it to have an infinite thrust
level and zero width so that you put an instantaneous
319
00:25:06,789 --> 00:25:07,039
pulse.
320
00:25:06,929 --> 00:25:10,750
It makes it easier for them to calculate where
the vehicle is going to go than if you get
321
00:25:10,750 --> 00:25:15,120
one that builds up kind of slow and goes down
kind of slow.
322
00:25:15,120 --> 00:25:22,120
The dribble volume, the volume that you have
between the valve seat and the injector phase
323
00:25:27,279 --> 00:25:33,669
when the engine shuts down, when the valve
closes that flow stops and that amount of
324
00:25:33,669 --> 00:25:35,340
propellant stays in there.
325
00:25:35,340 --> 00:25:40,909
Now, in a vacuum, when it gets down to the
vapor pressure starts boiling out and goes
326
00:25:40,909 --> 00:25:42,110
out through the chamber.
327
00:25:42,110 --> 00:25:48,840
And you have a refrigeration effect from that
boiling of the propellant.
328
00:25:48,840 --> 00:25:55,840
If the pulse width is too short then the refrigeration
effect will overcome the heating effect from
329
00:26:00,090 --> 00:26:05,140
that short pulse and you keep reducing the
temperature of the hardware.
330
00:26:05,140 --> 00:26:12,140
The colder the propellant gets the more heat
you have to put in the chemical reaction,
331
00:26:16,000 --> 00:26:19,520
when it first comes together, to get it to
ignite.
332
00:26:19,520 --> 00:26:22,980
You get an ignition delay in the thing and
then you start getting into hard starts if
333
00:26:22,980 --> 00:26:23,929
it gets too cold.
334
00:26:23,929 --> 00:26:30,929
So, we set our pulse width on the Shuttle
at 40 milliseconds.
335
00:26:31,870 --> 00:26:38,870
That was the neutral point at which the refrigeration
effect equaled the heating effect from the
336
00:26:40,799 --> 00:26:43,770
pulse, and so you would maintain the temperature.
337
00:26:43,770 --> 00:26:47,950
We later on went to 80 milliseconds on it
because we added the Veniers.
338
00:26:47,950 --> 00:26:52,100
That gave us a little bit of heat input.
339
00:26:52,100 --> 00:26:55,480
It's a pretty tough design in itself.
340
00:26:55,480 --> 00:27:02,480
The valve that we used for a 1000 pound rocket
on the Orbiter weighed less than the valves
341
00:27:03,210 --> 00:27:08,080
that we used on the Apollo program for 100
pound thruster.
342
00:27:08,080 --> 00:27:11,799
And what we did is we went to a pilot operated
valve.
343
00:27:11,799 --> 00:27:18,799
That was kind of my concept that I borrowed
from Sears Roebuck.
344
00:27:20,090 --> 00:27:23,730
If you ever take a washing machine apart on
a Sears Roebuck and you look at how the valve
345
00:27:23,730 --> 00:27:26,700
is designed, it is a pilot operated valve.
346
00:27:26,700 --> 00:27:29,350
And they use the water pressure to open the
valve.
347
00:27:29,350 --> 00:27:31,309
Well, I thought that was good way to go.
348
00:27:31,309 --> 00:27:37,169
You put a very small coil in there, a quick
acting coil and replace that rubber bellows
349
00:27:37,169 --> 00:27:42,940
that used on a Sears Roebuck washing machine
with a stainless steel diaphragm and you've
350
00:27:42,940 --> 00:27:44,840
got it made.
351
00:27:44,840 --> 00:27:50,730
Well, unfortunately the water pressure in
a house doesn't vary as much as the water
352
00:27:50,730 --> 00:27:55,990
hammer does on the Space Shuttle.
353
00:27:55,990 --> 00:28:00,460
So, before we got through with the design
of that valve, it got to be a very complex
354
00:28:00,460 --> 00:28:01,090
valve.
355
00:28:01,090 --> 00:28:05,289
And it was a very expensive valve but it worked.
356
00:28:05,289 --> 00:28:12,289
Probably the other thing we ought to say about
designing any system that is going to work
357
00:28:13,230 --> 00:28:19,659
with these hypergolic fuels, I mean they just
eat away at things like O ring seals.
358
00:28:19,659 --> 00:28:22,390
I mean it's just nasty stuff.
359
00:28:22,390 --> 00:28:27,270
And so, in addition to the mechanical problems
that Henry is talking about, you've got all
360
00:28:27,270 --> 00:28:30,289
the materials problems which just makes your
life harder.
361
00:28:30,289 --> 00:28:37,289
We really wanted to stay away from hypergols,
from the very strong acids and the very strong
362
00:28:40,250 --> 00:28:45,179
bases for the simple reason that there are
very few materials that are compatible with
363
00:28:45,179 --> 00:28:45,429
them.
364
00:28:45,179 --> 00:28:52,179
As a matter of fact, the main reason we went
to a hydrazine RCS in the beginning was to
365
00:28:53,260 --> 00:29:00,260
avoid having an expulsion system in the oxidizer
because we had no material available that
366
00:29:02,480 --> 00:29:07,789
you could put in there as a diaphragm to push
the propellants out that was compatible with
367
00:29:07,789 --> 00:29:12,570
N2O4 that you could make cycles with.
368
00:29:12,570 --> 00:29:16,940
We could have used metal bellows, but they
weren't very reliable.
369
00:29:16,940 --> 00:29:19,130
They were extremely heavy.
370
00:29:19,130 --> 00:29:22,990
And so we had to come up with a better system
than that.
371
00:29:22,990 --> 00:29:27,100
And then we kind of got to looking into putting
in screens in the system.
372
00:29:27,100 --> 00:29:29,539
And that was really a hard sell.
373
00:29:29,539 --> 00:29:32,110
I mean I spent lots of time with Aaron.
374
00:29:32,110 --> 00:29:39,110
I was convinced that system would work because
if you look at an automobile gas tank, every
375
00:29:39,630 --> 00:29:42,630
fuel tank on every automobile has got a sock
in it.
376
00:29:42,630 --> 00:29:49,630
That sock is about an inch and a half in diameter,
and it will suck every drop of fuel out of
377
00:29:52,010 --> 00:29:52,570
that gas tank.
378
00:29:52,570 --> 00:29:59,510
They putit in a little sump in there, and
it will just draw that tank dry before it
379
00:29:59,510 --> 00:30:02,169
will break down and let air go through it.
380
00:30:02,169 --> 00:30:05,890
I was convinced that we could build one of
those systems and make it work.
381
00:30:05,890 --> 00:30:09,529
But if you look at an automobile, you know
it goes over rough roads, it bounces, you've
382
00:30:09,529 --> 00:30:15,409
got G fields, you've got all kinds of forces
on that thing, and yet it works very good.
383
00:30:15,409 --> 00:30:20,409
The problem we had in trying to sell that
concept to the program, though, was how do
384
00:30:20,409 --> 00:30:22,250
you prove it?
385
00:30:22,250 --> 00:30:27,330
The only technique we had to prove it was
through analysis.
386
00:30:27,330 --> 00:30:34,330
And you're trying to prove that something
like that will work purely from analysis.
387
00:30:35,049 --> 00:30:39,070
And qualified by analysis was a hard, hard
sell.
388
00:30:39,070 --> 00:30:44,140
We, later on in a program, came up with techniques
where we could wrap tape around most of the
389
00:30:44,140 --> 00:30:47,510
screens in there so that we close up most
of the area.
390
00:30:47,510 --> 00:30:53,390
And so we would draw a propellant in, in very
small areas with aerospaces on top and prove
391
00:30:53,390 --> 00:30:59,130
that you could get down to a certain delta
P and cross it before it would break down
392
00:30:59,130 --> 00:31:00,990
to qualify our analysis.
393
00:31:00,990 --> 00:31:07,010
We still were not satisfied with that so we
made up a system with a glass tank, we put
394
00:31:07,010 --> 00:31:14,010
it on our vomit comet and flew it.
395
00:31:14,169 --> 00:31:17,070
And that was the only time where I ever road
that thing.
396
00:31:17,070 --> 00:31:22,409
If we had made one more time it would have
been all over for me.
397
00:31:22,409 --> 00:31:27,039
[LAUGHTER] But you get up 38,000 feet and
you make a dive on that thing.
398
00:31:27,039 --> 00:31:34,039
And you can maintain zero G in it through
that 30 second or 38 second period of time.
399
00:31:36,740 --> 00:31:42,649
And by expelling the right amount at the right
levels we could prove that it would work.
400
00:31:42,649 --> 00:31:46,360
And it has worked very, very well on all the
flights.
401
00:31:46,360 --> 00:31:53,360
In the future design of the spacecraft, what
is going to be the difference in the RCS system?
402
00:31:54,860 --> 00:31:58,289
Because every system is going to have to have
some kind of reaction control system.
403
00:31:58,289 --> 00:32:02,340
What do you think they are going to go with
in the future systems?
404
00:32:02,340 --> 00:32:09,340
I really believe that we ought to go with
either methane and LOX or alcohol and LOX.
405
00:32:10,580 --> 00:32:13,070
I think it's a much cleaner system.
406
00:32:13,070 --> 00:32:17,159
We developed that little piece of electric
igniter for the Shuttle Program.
407
00:32:17,159 --> 00:32:20,019
We never used it after we went away from those
systems.
408
00:32:20,019 --> 00:32:23,870
But you buy these little latch torches now
that you push a button and pull a trigger
409
00:32:23,870 --> 00:32:25,200
on it.
410
00:32:25,200 --> 00:32:32,200
And they light off most of the time, although
the last one I got didn't light too well.
411
00:32:34,169 --> 00:32:38,299
But we have good, reliable ignition systems
now.
412
00:32:38,299 --> 00:32:45,299
And I think that you can design a system now
that has the reliability that you need for
413
00:32:47,600 --> 00:32:48,809
a space system.
414
00:32:48,809 --> 00:32:55,809
Otherwise, we've done nothing in this country
since the Shuttle Program on developing [OVERLAPPING
415
00:32:56,250 --> 00:32:58,490
VOICES].
416
00:32:58,490 --> 00:33:05,490
The things you have got to remember is that
the thermal characteristics are very, very
417
00:33:07,390 --> 00:33:13,760
different in a vacuum than it is on earth.
418
00:33:13,760 --> 00:33:18,470
It is very different in the absence of gravity.
419
00:33:18,470 --> 00:33:21,470
You wouldn't think gravity would make any
difference in it but it does.
420
00:33:21,470 --> 00:33:24,029
You've got some fluid in the tank.
421
00:33:24,029 --> 00:33:25,840
You put some heat on the bottom of the tank.
422
00:33:25,840 --> 00:33:26,769
Where does heat go?
423
00:33:26,769 --> 00:33:27,630
It goes to the top of the tank.
424
00:33:27,630 --> 00:33:29,710
The top of the tank is always the hottest
part.
425
00:33:29,710 --> 00:33:34,010
When you've got a liquid in one G, you put
it in zero G, you put heat on the bottom of
426
00:33:34,010 --> 00:33:37,960
the tank, a bubble forms down there, it pushes
the liquid away from it and nothing comes
427
00:33:37,960 --> 00:33:39,269
out of the tank.
428
00:33:39,269 --> 00:33:42,090
Let me have some questions.
429
00:33:42,090 --> 00:33:49,090
I'm slightly confused on the fuel that the
system uses.
430
00:33:50,940 --> 00:33:56,580
Both RCS and the OMS use hydrazine or hypergolic?
431
00:33:56,580 --> 00:33:57,899
I'm confused.
432
00:33:57,899 --> 00:34:00,830
Hydrazine is N2H4.
433
00:34:00,830 --> 00:34:04,820
We use that as a monopropellant.
434
00:34:04,820 --> 00:34:09,480
A bipropellant earth storable.
435
00:34:09,480 --> 00:34:14,770
A monopropellant system you normally run it
over a catalytic bed and it decomposes.
436
00:34:14,770 --> 00:34:15,339
Yes.
437
00:34:15,339 --> 00:34:19,210
There are two monopropellants out there that
work very good.
438
00:34:19,210 --> 00:34:20,700
One is hydrogen peroxide.
439
00:34:20,700 --> 00:34:26,599
And if you can get it above 90% it gets a
little more stable.
440
00:34:26,599 --> 00:34:28,980
And the other one is hydrazine.
441
00:34:28,980 --> 00:34:32,480
Both of those you run through a catalyst.
442
00:34:32,480 --> 00:34:37,179
When it hits a catalyst you get the reaction
out of it and it breaks down.
443
00:34:37,179 --> 00:34:44,179
The hydrogen peroxide breaks down to steam
and oxygen, and hydrazine breaks down to hydrogen
444
00:34:48,639 --> 00:34:55,639
and ammonia, NH3.
445
00:34:57,630 --> 00:35:02,089
But both of those give you hot gases then
for propulsion.
446
00:35:02,089 --> 00:35:07,480
You mix that with an acid and you get combustion.
447
00:35:07,480 --> 00:35:12,030
And we used aerozine 50 which I mentioned.
448
00:35:12,030 --> 00:35:18,589
Aerozine 50 was 50% hydrazine and 50% unsymmetrical
dimethylhydrazine.
449
00:35:18,589 --> 00:35:22,710
Monomethylhydrazine is just that, monomethylhydrazine.
450
00:35:22,710 --> 00:35:28,310
It is a lot more stable than is hydrazine.
451
00:35:28,310 --> 00:35:33,190
It has a wider freezing /boiling point than
hydrazine.
452
00:35:33,190 --> 00:35:39,450
Hydrazine has a lot of the characteristics
of water as far as density, freezing and boiling.
453
00:35:39,450 --> 00:35:44,000
It will freeze at about the same temperature
as water, it will boil at about the same temperature
454
00:35:44,000 --> 00:35:48,420
as water and it has almost the same density
as water.
455
00:35:48,420 --> 00:35:54,060
Monomethylhydrazine has a little bit slightly
less density, it gives you a slightly better
456
00:35:54,060 --> 00:36:00,720
performance but it freezes at like minus 63
degrees or something like that.
457
00:36:00,720 --> 00:36:05,750
Monomethylhydrazine and nitrogen tetroxide.
458
00:36:05,750 --> 00:36:07,690
The same thing for the OMS.
459
00:36:07,690 --> 00:36:14,690
Now, one of the things we do is we put about
four-tenths of a percent of nitric oxide in
460
00:36:17,400 --> 00:36:21,500
the nitrogen tetroxide to keep the tanks from
breaking.
461
00:36:21,500 --> 00:36:24,170
We have titanium tanks.
462
00:36:24,170 --> 00:36:28,910
And on the Apollo Program we got into a very
serious problem because a tank started exploding.
463
00:36:28,910 --> 00:36:35,910
It turned out with aerozine 50 or monopropellant
hydrazine, we had a little bit of water in
464
00:36:37,130 --> 00:36:40,500
there and that gave off a little bit of free
hydrogen.
465
00:36:40,500 --> 00:36:45,020
And that free hydrogen, titanium just does
not like hydrogen.
466
00:36:45,020 --> 00:36:49,040
How many people have taken fraction mechanics?
467
00:36:49,040 --> 00:36:50,810
Well, fraction mechanics really started from
that.
468
00:36:50,810 --> 00:36:53,520
That's when we started working with a gentleman
called Dr.
469
00:36:53,520 --> 00:36:54,550
Tiffany at Boeing.
470
00:36:54,550 --> 00:36:59,619
We worked with the whole world on that problem.
471
00:36:59,619 --> 00:37:02,140
That's how fraction mechanics really got started.
472
00:37:02,140 --> 00:37:05,560
You were going to ask something.
473
00:37:05,560 --> 00:37:10,630
While we're talking about fractions, one of
the other problems of dealing with these hypergolic
474
00:37:10,630 --> 00:37:12,520
fuels is the freezing problem.
475
00:37:12,520 --> 00:37:15,560
Maybe we will talk a little bit about that.
476
00:37:15,560 --> 00:37:22,560
Because, unlike water, when the hydrazine
freezes it shrinks.
477
00:37:23,170 --> 00:37:29,000
And so if you imagine that you've got hydrazine
liquid in a line under pressure and now it
478
00:37:29,000 --> 00:37:31,540
gets too cold so it freezes.
479
00:37:31,540 --> 00:37:36,140
And now that leaves a little bit of free volume
so you get more liquid that comes in there
480
00:37:36,140 --> 00:37:37,240
and that will freeze.
481
00:37:37,240 --> 00:37:42,589
Until finally the entire line is clogged up
with solid hydrazine.
482
00:37:42,589 --> 00:37:47,220
Now, when it warms up it expands and you crack
the line.
483
00:37:47,220 --> 00:37:51,170
And now you've got a hypergolic leak which
is really bad news.
484
00:37:51,170 --> 00:37:58,170
So, in fact, maintaining thermal control of
the OMS and RCS propellant lines becomes a
485
00:37:58,800 --> 00:37:59,660
very critical issue.
486
00:37:59,660 --> 00:38:04,940
And there are heating coils all over the place
and thermostats.
487
00:38:04,940 --> 00:38:11,940
And so, again, you don't just have a propulsion
system in the systems engineering that we
488
00:38:15,270 --> 00:38:18,510
talked about.
489
00:38:18,510 --> 00:38:25,510
It affects the thermal, the electrical system,
because all these things are inner-related.
490
00:38:27,760 --> 00:38:34,760
If you lose an electrical system so that you
cannot run the heaters then you run the risk
491
00:38:34,900 --> 00:38:37,089
of losing your propellant system.
492
00:38:37,089 --> 00:38:39,700
And so then you have to have redundant heaters
and so on.
493
00:38:39,700 --> 00:38:42,950
And it gets more and more complicated.
494
00:38:42,950 --> 00:38:47,359
That was a major, major problem we had on
Apollo 13.
495
00:38:47,359 --> 00:38:48,839
We didn't have enough power.
496
00:38:48,839 --> 00:38:50,859
We had to turn everything off quick.
497
00:38:50,859 --> 00:38:57,859
And trying to get those people to let that
temperature go down out of limits was not
498
00:38:58,450 --> 00:38:59,230
easy.
499
00:38:59,230 --> 00:39:04,520
And I remember sitting down and spending an
entire night running out the thermal calculations
500
00:39:04,520 --> 00:39:10,609
and calculating out when we could turn the
heaters off or we could keep the service module
501
00:39:10,609 --> 00:39:16,220
off of that vehicle and not freeze the propellant
and the RCS on the command module.
502
00:39:16,220 --> 00:39:18,079
And then I got really, really worried.
503
00:39:18,079 --> 00:39:22,599
I gave myself four degrees above freezing
on that system, and I missed it two degrees.
504
00:39:22,599 --> 00:39:26,770
It got two degrees colder than we had planned.
505
00:39:26,770 --> 00:39:32,390
The design of the RCS system was very, very
complicated.
506
00:39:32,390 --> 00:39:39,390
How many RCS specialists do we have on the
Shuttle, 40?
507
00:39:39,430 --> 00:39:43,849
Thirty-eight primary and four Vernier.
508
00:39:43,849 --> 00:39:47,369
And so it's a very complicated system in designing
it.
509
00:39:47,369 --> 00:39:49,640
It had a lot of requirements placed on it.
510
00:39:49,640 --> 00:39:55,190
On the other hand, the OMS engine, as I recall,
we have never had a failure on the OMS engine.
511
00:39:55,190 --> 00:39:57,540
The OMS engine has been very, very successful.
512
00:39:57,540 --> 00:40:01,390
It is a very straightforward program.
513
00:40:01,390 --> 00:40:07,579
By getting the combustion close to the injector
on the OMS then we could make the chamber
514
00:40:07,579 --> 00:40:09,920
small on the OMS.
515
00:40:09,920 --> 00:40:15,970
And, by making the chamber very small on the
OMS, then you could cool it.
516
00:40:15,970 --> 00:40:21,160
You could put cooling channels down the chamber
and run the fuel down there and keep the chamber
517
00:40:21,160 --> 00:40:22,810
cool so it wouldn't burn out.
518
00:40:22,810 --> 00:40:28,119
Now, we also did the same thing on the RCS
a little bit different.
519
00:40:28,119 --> 00:40:30,599
The RCS is a buried installation.
520
00:40:30,599 --> 00:40:37,369
We have to run that engine for 500 seconds
or more if we want to use it for de-orbit
521
00:40:37,369 --> 00:40:40,180
in case the OMS plays out sometimes.
522
00:40:40,180 --> 00:40:45,040
That engine has to stay together on these
very, very short burns.
523
00:40:45,040 --> 00:40:52,040
It also has to stay together on these very,
very long burns with fluctuating inlet pressures
524
00:40:52,800 --> 00:40:55,950
and fluctuating mixture ratios.
525
00:40:55,950 --> 00:41:02,950
We found that if we make a very, very short
chamber -- And that's why when you look at
526
00:41:03,109 --> 00:41:07,460
the RCS it is a big chamber, it is very short.
527
00:41:07,460 --> 00:41:13,960
We could put enough fuel down the walls of
that chamber to effectively cool the chamber
528
00:41:13,960 --> 00:41:19,730
so it would only go up steady states to a
certain safe temperature and still have good
529
00:41:19,730 --> 00:41:21,180
performance out of it.
530
00:41:21,180 --> 00:41:26,030
So, we put a lot of fuel down the walls on
it.
531
00:41:26,030 --> 00:41:33,030
Looking in this direction, if this is the
injector plate, the holes around the outer
532
00:41:34,410 --> 00:41:37,339
most layer, those are all fuel.
533
00:41:37,339 --> 00:41:44,250
So, you basically get a fuel bath coming along
that actually comes in contact.
534
00:41:44,250 --> 00:41:51,250
And if you have a fuel-rich mixture, the same
as in a car, the fuel mixture burns cooler.
535
00:41:51,520 --> 00:41:56,500
The thing that you're really afraid of, in
fact, you have to deal with a lot of contingencies
536
00:41:56,500 --> 00:42:03,500
on this system, what happens if you get a
clog in one of your feed lines?
537
00:42:03,920 --> 00:42:10,920
The worst situation you can get in is that
you get a clog in your fuel inlet line, and
538
00:42:12,260 --> 00:42:16,030
that gives you an oxidizer-rich mixture which
burns hot.
539
00:42:16,030 --> 00:42:20,079
And you can then actually get a melt through.
540
00:42:20,079 --> 00:42:24,130
And so you've got to shut your engine down
in a hurry if that happens.
541
00:42:24,130 --> 00:42:28,099
These are very, very small orifices, and a
lot of them around the outside of it.
542
00:42:28,099 --> 00:42:35,099
And if you get a couple of these orifices
plugged then that becomes a hot spot on the
543
00:42:35,560 --> 00:42:36,829
side of the chamber.
544
00:42:36,829 --> 00:42:39,790
And we used columbium, which has very poor
heat transfer.
545
00:42:39,790 --> 00:42:45,359
We used molybdenum on Apollo which has good
heat transfer.
546
00:42:45,359 --> 00:42:52,359
To return to your point about the possibility
of using the RCS as a backup for reentry,
547
00:42:54,990 --> 00:43:01,990
what prevents one from using a series of relatively
short burns [carried on the mass?] of the
548
00:43:02,990 --> 00:43:05,630
Orbiter to smooth out the velocity chain?
549
00:43:05,630 --> 00:43:12,630
Why do you have to have a single file of second
burn?
550
00:43:15,450 --> 00:43:21,980
Before you start to burn, to come back in,
how much time you can put in between those
551
00:43:21,980 --> 00:43:28,980
and how short, a 1,000 pound thruster for
deorbit takes a fairly long burn.
552
00:43:29,180 --> 00:43:36,180
And the engine goes to steady state fairly
quick, you know, in a matter of 20 seconds.
553
00:43:38,930 --> 00:43:45,930
[UNINTELLIGIBLE PHRASE] We ran RCS engines
for the Shuttle up to an hour and a half on
554
00:43:47,250 --> 00:43:51,250
a single burn.
555
00:43:51,250 --> 00:43:58,250
[UNINTELLIGIBLE PHRASE] Even though you put
it in multiple burns you still have to have
556
00:44:02,630 --> 00:44:04,390
fairly long pulse widths on each one of them.
557
00:44:04,390 --> 00:44:06,599
And that impacts the guidance very, very badly.
558
00:44:06,599 --> 00:44:13,599
Let me help with a little orbital mechanics.
559
00:44:14,609 --> 00:44:21,609
We talked about this before.
560
00:44:25,099 --> 00:44:31,390
You're in orbit.
561
00:44:31,390 --> 00:44:38,390
When you do a burn, you can do a retrograde
burn which lowers the other side of your orbit
562
00:44:47,089 --> 00:44:50,910
so that now becomes the perigee.
563
00:44:50,910 --> 00:44:56,869
The thing is, from orbital mechanics, the
most efficient way to do a burn is to have,
564
00:44:56,869 --> 00:45:02,810
like Henry said, an infinite thrust with a
zero pulse width.
565
00:45:02,810 --> 00:45:05,270
You do what they call an impulsive burn.
566
00:45:05,270 --> 00:45:09,260
But, in the real world, that never happens.
567
00:45:09,260 --> 00:45:14,160
Now, it is 45 minutes from here to here, it's
a 90 minute orbit.
568
00:45:14,160 --> 00:45:21,160
Now, when you have two OMS engines, a typical
deorbit burn lasts two to two and a half minutes.
569
00:45:22,500 --> 00:45:25,819
You're burning over this segment.
570
00:45:25,819 --> 00:45:28,550
It's pretty close to an impulsive burn.
571
00:45:28,550 --> 00:45:32,020
You lose one OMS engine and now you have to
double it.
572
00:45:32,020 --> 00:45:33,960
Now you're up to a five minute burn.
573
00:45:33,960 --> 00:45:39,210
But, if you lose your second OMS engine and
now you have to do an RCS deorbit, now you're
574
00:45:39,210 --> 00:45:42,740
getting into a 10, 15 minute burn.
575
00:45:42,740 --> 00:45:46,780
And so you're actually really far away from
optimum.
576
00:45:46,780 --> 00:45:49,599
And the burn gets much less efficient.
577
00:45:49,599 --> 00:45:56,410
And so if you have plenty of propellant you're
fine, but if you're low on propellant you
578
00:45:56,410 --> 00:45:58,800
need to worry about the efficiency of your
burn.
579
00:45:58,800 --> 00:46:03,859
If you were to do a little bit of a burn and
then shut it down to let your engines cool
580
00:46:03,859 --> 00:46:07,569
off and then you try to complete the burn
around here, now it has gotten really, really
581
00:46:07,569 --> 00:46:14,569
inefficient and you might run out of propellant.
582
00:46:15,210 --> 00:46:22,210
We spent an enormous amount of time with our
orbital mechanics people and our guidance
583
00:46:23,010 --> 00:46:28,000
people trying to get the OMS strut down as
low as we could get it.
584
00:46:28,000 --> 00:46:33,839
Because the lower you can get it the smaller
the hardware, the lighter the weight of the
585
00:46:33,839 --> 00:46:36,810
hardware and the performance is essentially
the same.
586
00:46:36,810 --> 00:46:43,349
The ISP for a 3,000 pound engine is essentially
the same as it is for a 20,000 or maybe even
587
00:46:43,349 --> 00:46:47,900
a little bit higher for 3,000.
588
00:46:47,900 --> 00:46:50,310
We had 5,000 pound thrust in there.
589
00:46:50,310 --> 00:46:52,410
We had 4,000 pound thrust in there.
590
00:46:52,410 --> 00:46:54,339
I think we finally wound up with 3,500.
591
00:46:54,339 --> 00:47:01,339
Been left up to me, I think we could have
done it with a 1,500 pound thrust engine.
592
00:47:01,829 --> 00:47:05,800
But we compromised.
593
00:47:05,800 --> 00:47:06,450
Yes.
594
00:47:06,450 --> 00:47:13,450
Professor Cohen once mentioned that some people
suggested putting some RCS thrusters on the
595
00:47:15,010 --> 00:47:22,010
edge of the wing tips, but that would be very
difficult after the design was finalized.
596
00:47:22,650 --> 00:47:29,650
All of our early configurations that we had,
we had the RCS pods out on the wing tips.
597
00:47:29,700 --> 00:47:33,430
It made the RCS very efficient.
598
00:47:33,430 --> 00:47:40,430
Our RCS was the OMS at one time, and we had
it all out on the wing tips.
599
00:47:40,510 --> 00:47:44,510
It didn't make our structures friends too
happy at first because that puts a lot of
600
00:47:44,510 --> 00:47:49,300
mass out into the wings and they didn't like
it too much, but after they got looking at
601
00:47:49,300 --> 00:47:54,400
it that turned out that really wasn't much
of a driver.
602
00:47:54,400 --> 00:47:57,040
It made the RCS very efficient.
603
00:47:57,040 --> 00:48:04,040
The thing that kind of changed that is when
we put the big payload bay on the inside of
604
00:48:04,109 --> 00:48:08,440
the vehicle and then we had to put a big OMS
pod on there.
605
00:48:08,440 --> 00:48:15,440
And then to put the RCS pods out on a wing
tip of a delta system out there just didn't
606
00:48:16,280 --> 00:48:18,839
weigh out good.
607
00:48:18,839 --> 00:48:24,190
It was more efficient from a weight standpoint
to put the OMS and RCS together because we
608
00:48:24,190 --> 00:48:26,150
actually had those two interconnected.
609
00:48:26,150 --> 00:48:30,540
If we have to do an OMS burn with the RCS,
we can take the propellant out of the OMS
610
00:48:30,540 --> 00:48:35,589
tank to feed the RCS.
611
00:48:35,589 --> 00:48:40,260
And so it just made a more efficient system
to bring it all in.
612
00:48:40,260 --> 00:48:41,720
We had another requirement.
613
00:48:41,720 --> 00:48:48,720
When we went to the acid-based propellants,
we had a requirement that we had to have removable
614
00:48:49,420 --> 00:48:49,740
pods.
615
00:48:49,740 --> 00:48:55,170
You had to be able to take the propulsion
system off of the orbiter and take it over
616
00:48:55,170 --> 00:49:00,569
to another facility to rework it because we
knew we were going to have a lot of work and
617
00:49:00,569 --> 00:49:07,569
rework on those systems, at least early on.
618
00:49:09,690 --> 00:49:10,829
You had a question right here.
619
00:49:10,829 --> 00:49:17,829
To what extent can you change orbits due to
a higher or lower orbit [UNINTELLIGIBLE]?
620
00:49:20,309 --> 00:49:27,309
That is very limited, but we do have the capability
to go up and down in orbit.
621
00:49:30,710 --> 00:49:32,210
I don't know, maybe 50 miles.
622
00:49:32,210 --> 00:49:32,700
I don't know.
623
00:49:32,700 --> 00:49:34,040
I don't have a good answer.
624
00:49:34,040 --> 00:49:34,619
I don't remember that.
625
00:49:34,619 --> 00:49:36,589
That has been too long ago.
626
00:49:36,589 --> 00:49:43,589
With a full load you have a few hundred feet
per second, I would have to go and look up,
627
00:49:45,500 --> 00:49:47,079
you cannot make the plane change.
628
00:49:47,079 --> 00:49:49,450
No, plane changes are out.
629
00:49:49,450 --> 00:49:56,450
But we certainly have gone from, let's see,
like 180 nautical mile orbits down to a 105
630
00:50:01,910 --> 00:50:02,270
mile.
631
00:50:02,270 --> 00:50:06,540
I remember one flight where we did that.
632
00:50:06,540 --> 00:50:13,540
To go up, you know, what you really want to
do is, of course, use your main propulsion
633
00:50:13,849 --> 00:50:17,260
system to get into the right orbit that you
want to go to.
634
00:50:17,260 --> 00:50:21,910
Then, if you're going to do a rendezvous,
you have to change the height a little bit.
635
00:50:21,910 --> 00:50:28,730
But you typically try to get orbit insertion
within about 20 nautical miles, so about 40
636
00:50:28,730 --> 00:50:35,170
kilometers radius of your ultimate intended
orbit.
637
00:50:35,170 --> 00:50:42,170
For some special missions, like I was on one
mission where we were up at about 180 nautical
638
00:50:42,940 --> 00:50:49,170
miles doing various operations, but then the
last couple of days they wanted to look at
639
00:50:49,170 --> 00:50:55,390
the interaction of the Orbiter with the atomic
oxygen and nitrogen which causes this orbiter
640
00:50:55,390 --> 00:50:59,170
glow phenomena, which maybe some of you have
heard about.
641
00:50:59,170 --> 00:51:05,369
We had to go down to about 105 nautical miles,
which is about as low as you can go and stay
642
00:51:05,369 --> 00:51:09,069
in orbit for more than a day or so.
643
00:51:09,069 --> 00:51:15,530
And so, yeah, that was OK because that was
just you're doing part of your deorbit burn
644
00:51:15,530 --> 00:51:17,170
but then you stop.
645
00:51:17,170 --> 00:51:21,890
What you wouldn't want to do is go to a 105
mile orbit and then go up, and then you would
646
00:51:21,890 --> 00:51:23,180
have to come all the way down again.
647
00:51:23,180 --> 00:51:27,910
I think we will take one more question and
go to break.
648
00:51:27,910 --> 00:51:33,920
It is awfully easy to decrease the orbit because
you're using part of the energy that you have
649
00:51:33,920 --> 00:51:35,559
to use to come back home anyway.
650
00:51:35,559 --> 00:51:38,020
When you start trying to go up is when you're
adding.
651
00:51:38,020 --> 00:51:40,329
But we have a lot of contingency propellant
onboard.
652
00:51:40,329 --> 00:51:44,910
We've got contingent propellant in case the
main engines shut off early.
653
00:51:44,910 --> 00:51:46,790
Then you have to use the RCS.
654
00:51:46,790 --> 00:51:52,069
If you've got a docking mission we've got
propellant in there for three or four attempts
655
00:51:52,069 --> 00:51:55,329
at docking and things like that.
656
00:51:55,329 --> 00:51:59,680
There is extra propellant that you can use
to give you a little bit of a boost.
657
00:51:59,680 --> 00:52:01,720
You had a question here.
658
00:52:01,720 --> 00:52:08,720
Going back to the comment that was made about
the [UNINTELLIGIBLE PHRASE] and presenting
659
00:52:22,119 --> 00:52:24,089
a hazard that way, what kind of feedback did
the crew have when something like that was
660
00:52:24,089 --> 00:52:24,339
happening?
661
00:52:24,119 --> 00:52:24,380
Were there sensors in that system [UNINTELLIGIBLE
PHRASE]?
662
00:52:24,380 --> 00:52:24,630
I don't hear too well.
663
00:52:24,550 --> 00:52:30,460
The question is what sort of sensors do we
have for the operation of the engines?
664
00:52:30,460 --> 00:52:32,180
There are pressure sensors.
665
00:52:32,180 --> 00:52:34,230
There are temperature sensors.
666
00:52:34,230 --> 00:52:41,230
Again, remember when we were talking earlier,
though, sensors don't always tell the truth.
667
00:52:41,410 --> 00:52:43,119
Sometimes you can get sensor failures.
668
00:52:43,119 --> 00:52:46,220
And so we spent a lot of time practicing.
669
00:52:46,220 --> 00:52:49,490
And you work out all the different scenarios.
670
00:52:49,490 --> 00:52:52,030
This is what you will see if you have a real
failure.
671
00:52:52,030 --> 00:52:54,720
This is what you will see if you have a sensor
failure.
672
00:52:54,720 --> 00:53:00,800
And, before you shut down a good working engine,
you would like to confirm the fact that it
673
00:53:00,800 --> 00:53:04,190
is really an engine problem, not a sensor
problem.
674
00:53:04,190 --> 00:53:10,510
On the other hand, you don't want to take
a chance that you're going to get into an
675
00:53:10,510 --> 00:53:15,190
oxidizer-rich situation and blow up your engine.
676
00:53:15,190 --> 00:53:22,190
You practice and after a while get pretty
good at diagnosing the problems fairly quickly.
677
00:53:23,890 --> 00:53:30,890
The computer doesn't normally shut down the
OMS engine on its own.
678
00:53:32,240 --> 00:53:35,589
The computer will not shut down any of the
propulsion systems on its own.
679
00:53:35,589 --> 00:53:41,280
It will shut down the main engine, but none
of these will it shut down on its own.
680
00:53:41,280 --> 00:53:44,390
Somebody has got to take some action to shut
it down.
681
00:53:44,390 --> 00:53:49,569
We get an awful lot of data on the ground,
too, that you don't have in the cockpit that
682
00:53:49,569 --> 00:53:54,790
you can look at different instruments and
backup things and try to understand where
683
00:53:54,790 --> 00:53:57,119
there is a sensor failure.
684
00:53:57,119 --> 00:54:00,589
Any other questions on OMS/RCS?
685
00:54:00,589 --> 00:54:07,589
During entry, when you're coming down using
the RCS for like trajectory guidance before
686
00:54:09,460 --> 00:54:15,300
your aerosurfaces are usable, how much propellant
would you typically use?
687
00:54:15,300 --> 00:54:17,420
Is there like a certain percentage that would
be average?
688
00:54:17,420 --> 00:54:19,599
That's a pretty low percentage, and I don't
recall.
689
00:54:19,599 --> 00:54:23,220
That has been a long time now, and I don't
recall the numbers.
690
00:54:23,220 --> 00:54:26,020
But I would say it's less than 10% of the
propellant.
691
00:54:26,020 --> 00:54:27,089
What did you say?
692
00:54:27,089 --> 00:54:27,619
About 10%.
693
00:54:27,619 --> 00:54:34,619
Well, at least that ought to be a pretty good
number.
694
00:54:34,640 --> 00:54:40,760
[LAUGHTER] It's not a lot of propellant come
back in on it.
695
00:54:40,760 --> 00:54:43,329
The vehicle is a fairly stable vehicle.
696
00:54:43,329 --> 00:54:48,359
Now, on Columbia, I guess they either ran
out of propellant or just about ran out of
697
00:54:48,359 --> 00:54:50,970
propellant on it trying to hold it.
698
00:54:50,970 --> 00:54:56,670
RCS was doing all it could to try to hold
that vehicle on course after it started picking
699
00:54:56,670 --> 00:54:59,130
up drag on one side.
700
00:54:59,130 --> 00:55:06,130
And we actually did have procedures in place
for what we called a no RCS entry if you had
701
00:55:08,809 --> 00:55:10,849
run out of propellant entirely.
702
00:55:10,849 --> 00:55:17,049
I don't know if it would have worked.
703
00:55:17,049 --> 00:55:24,049
You tried to get it into a stable aerodynamic
situation as possible and just hold it there.
704
00:55:24,670 --> 00:55:30,520
I never had to actually do it.
705
00:55:30,520 --> 00:55:32,400
Anymore OMS/RCS questions?
706
00:55:32,400 --> 00:55:39,069
Otherwise, why don't we take a little break
and then we will come back for APU/hydraulics.
707
00:55:39,069 --> 00:55:45,640
Two minute break.
708
00:55:45,640 --> 00:55:52,220
Thank you all.
709
00:55:52,220 --> 00:55:56,599
Appreciate it.
710
00:55:56,599 --> 00:56:03,170
You're not finished.
711
00:56:03,170 --> 00:56:05,369
APU/hydraulics.
712
00:56:05,369 --> 00:56:11,829
And I guess I need to point out some acronyms.
713
00:56:11,829 --> 00:56:16,559
Calling the APU an APU was the biggest mistake
we ever made.
714
00:56:16,559 --> 00:56:23,299
That gave me more grief than any other system
that I had to deal with, the acronym.
715
00:56:23,299 --> 00:56:27,230
APU stands for auxiliary power unit.
716
00:56:27,230 --> 00:56:31,790
And the Aerospace Safety Advisory Committee
-- I will tell you, Henry, my kids growing
717
00:56:31,790 --> 00:56:34,359
up used to think it was a three letter bad
word.
718
00:56:34,359 --> 00:56:36,700
I mean they thought APU was a bad word.
719
00:56:36,700 --> 00:56:40,480
[LAUGHTER] Because every time I got a call
there was something wrong with it.
720
00:56:40,480 --> 00:56:47,480
If we would have called it primary power unit
then we would have had a lot less grief in
721
00:56:49,460 --> 00:56:54,839
trying to defend it to the outside world.
722
00:56:54,839 --> 00:57:01,839
APU/hydraulics, like the OMS and RCS, all
of our first activity was directed toward
723
00:57:02,950 --> 00:57:08,690
keeping the operational cost down low, keeping
the maintenance cost down low.
724
00:57:08,690 --> 00:57:15,690
And we looked at those kinds of systems that
gave you clean propellants, easy propellants
725
00:57:17,160 --> 00:57:24,160
to deal with and you didn't have to worry
about the strong bases and strong acids to
726
00:57:27,780 --> 00:57:31,799
work with.
727
00:57:31,799 --> 00:57:38,750
Later on, as time went on, we got more into
looking at what we could do cheap from a development
728
00:57:38,750 --> 00:57:45,750
standpoint and let the operational cost float,
because it is obvious that the money was not
729
00:57:48,740 --> 00:57:55,740
going to be there to put into a big development
program.
730
00:58:01,280 --> 00:58:08,280
The control of the vehicle in the atmosphere
was a major, major activity to try to find
731
00:58:13,000 --> 00:58:19,000
out what you could get by with versus what
you would like to have.
732
00:58:19,000 --> 00:58:26,000
You try to move these huge barn doors fast
and a whole lot, there are huge forces on
733
00:58:26,339 --> 00:58:27,260
those things.
734
00:58:27,260 --> 00:58:32,700
It takes lots and lots of power to move them
and move them quick.
735
00:58:32,700 --> 00:58:37,670
And our aero people and our guidance people
would like to have, like we were talking a
736
00:58:37,670 --> 00:58:41,049
while ago, an instantaneous impulse into that
vehicle.
737
00:58:41,049 --> 00:58:44,559
When it starts to drift a little bit and they
want to move it some other way they like to
738
00:58:44,559 --> 00:58:48,740
put an impulse in there and just kick it right
back where it is supposed to be instantly.
739
00:58:48,740 --> 00:58:55,740
But that becomes impractical when you look
at these kinds of systems.
740
00:59:01,380 --> 00:59:04,020
We started out with dual tandem actuators.
741
00:59:04,020 --> 00:59:11,020
Now, dual tandem actuators is something that
fail op fail safe criteria.
742
00:59:11,640 --> 00:59:16,930
In other words, you had two pistons and one
actuator driven by two different hydraulic
743
00:59:16,930 --> 00:59:20,420
systems and you would move them together.
744
00:59:20,420 --> 00:59:25,230
When you start looking at all of the failure
modes associated with dual tandem actuators,
745
00:59:25,230 --> 00:59:31,630
even though it meets the fail op fail safe
criteria that makes the safety people happy
746
00:59:31,630 --> 00:59:38,430
and the people that are looking at the buzz
words, it actually was making the system less
747
00:59:38,430 --> 00:59:38,950
safe.
748
00:59:38,950 --> 00:59:45,020
Was that because you had a single passenger
[using up?] all the hydraulic fluid?
749
00:59:45,020 --> 00:59:45,309
No.
750
00:59:45,309 --> 00:59:50,240
What happened in a dual tandem actuator, in
order to get them to work well, if you busted
751
00:59:50,240 --> 00:59:53,369
an actuator then that became a big sponge?
752
00:59:53,369 --> 00:59:59,270
You didn't have any way to take that space
out.
753
00:59:59,270 --> 01:00:06,270
Trying to have that actuator work when the
other half went out made it very, very difficult,
754
01:00:06,780 --> 01:00:11,869
from a design standpoint, to come up with
a system that you could lock it in place.
755
01:00:11,869 --> 01:00:18,549
And we even had designs where if one hydraulic
system failed that that shaft would actually
756
01:00:18,549 --> 01:00:20,290
lock itself.
757
01:00:20,290 --> 01:00:22,299
With the absence of pressure it would lock
itself.
758
01:00:22,299 --> 01:00:27,500
Well, that becomes a failure in itself because
if that mechanism fails then you've got a
759
01:00:27,500 --> 01:00:29,030
locked actuator.
760
01:00:29,030 --> 01:00:34,450
One thing you cannot stand on an aeroplane
is for an actuator not to move.
761
01:00:34,450 --> 01:00:37,299
We were finally able to convince the people.
762
01:00:37,299 --> 01:00:44,049
And Aaron was having lots and lots problems
about that time because all of the weight
763
01:00:44,049 --> 01:00:45,500
was in the backend of the vehicle.
764
01:00:45,500 --> 01:00:50,299
The dual tandem actuators were extremely heavy
and the backend of the vehicle was getting
765
01:00:50,299 --> 01:00:54,589
too heavy, so we actually went to a single
actuator.
766
01:00:54,589 --> 01:01:00,569
And we put switching valves in there where
we could switch any one of the four APU systems
767
01:01:00,569 --> 01:01:04,599
into that actuator.
768
01:01:04,599 --> 01:01:11,599
And we had four APUs at that time.
769
01:01:12,329 --> 01:01:18,319
Weight was still a problem so we were able
to convince the community that we could live
770
01:01:18,319 --> 01:01:25,319
with three APUs and have one APU fail and
come home normal mode with two.
771
01:01:26,109 --> 01:01:32,430
And if you had two failures you could still
land the vehicle with one actuator.
772
01:01:32,430 --> 01:01:38,460
You lost a whole bunch of systems but you
could still land it with one APU.
773
01:01:38,460 --> 01:01:44,109
And we almost did that one time, because if
someone would have told me that we would ever
774
01:01:44,109 --> 01:01:51,109
have two failures of the same type on the
same flight of the nature that we had I would
775
01:01:52,319 --> 01:01:53,609
have never believed it.
776
01:01:53,609 --> 01:01:57,740
But we came home on one flight with two APUs
burning.
777
01:01:57,740 --> 01:02:01,190
We had a fire in both of the APUs.
778
01:02:01,190 --> 01:02:06,039
And the reason for that, after the fact again,
is very, very simple.
779
01:02:06,039 --> 01:02:08,299
We went through a very good quality program.
780
01:02:08,299 --> 01:02:15,299
We did everything that we needed to on those
things only to find out that we had not planned
781
01:02:16,289 --> 01:02:23,260
on landing the vehicle in California and piggy
backing it back down to the Cape over and
782
01:02:23,260 --> 01:02:24,650
over again.
783
01:02:24,650 --> 01:02:30,880
What happens when you do that is that you
land the vehicle, there is a little bit of
784
01:02:30,880 --> 01:02:36,010
residual APU hydrazine in those tubes between
the valves and the injector.
785
01:02:36,010 --> 01:02:39,589
You go back up into a vacuum or low pressure.
786
01:02:39,589 --> 01:02:41,099
All the air goes out of the system.
787
01:02:41,099 --> 01:02:43,539
And then we come and land in Florida.
788
01:02:43,539 --> 01:02:44,690
It is always humid in Florida.
789
01:02:44,690 --> 01:02:46,609
There is a lot of moisture there.
790
01:02:46,609 --> 01:02:52,010
And as that moist air started feeding back
in the engine, it went up past the [cat?]
791
01:02:52,010 --> 01:02:59,010
bed and got in those tubes between the valve
and the injector and set up a very, very corrosive
792
01:03:00,799 --> 01:03:07,799
environment of residual hydrazine and water.
793
01:03:08,869 --> 01:03:10,809
And that gave off free hydrogen.
794
01:03:10,809 --> 01:03:14,440
And you had hydrogen or intergranular corrosion
in those tubes.
795
01:03:14,440 --> 01:03:21,440
And we had two of them break on the same flight,
but it worked.
796
01:03:21,559 --> 01:03:28,559
We spent an awful lot of time looking at power
sources to power the hydraulic systems.
797
01:03:31,720 --> 01:03:37,260
And we even looked at going with all electrical
systems.
798
01:03:37,260 --> 01:03:43,170
DOD had some very good fuel cells out there
that had a lot of promise.
799
01:03:43,170 --> 01:03:50,170
It put an awful lot of power at that time.
800
01:03:50,569 --> 01:03:53,910
Let me just digress a little bit and talk
about shuttle fuel cells.
801
01:03:53,910 --> 01:03:57,140
I don't think anybody can cover that.
802
01:03:57,140 --> 01:03:59,230
On Gemini the fuel cells never did work.
803
01:03:59,230 --> 01:04:06,230
We always came back with half voltage or partial
voltage and most of the fuel cells out.
804
01:04:06,819 --> 01:04:13,819
On Apollo, it only took 14 PhDs to start them
and shut them down.
805
01:04:14,829 --> 01:04:18,500
And then you couldn't start them again.
806
01:04:18,500 --> 01:04:25,500
On the Space Shuttle, those fuel cells, it
is just a very, very good battery with the
807
01:04:27,819 --> 01:04:32,309
chemicals stored external to the battery.
808
01:04:32,309 --> 01:04:35,559
They would make an outstanding DC welder.
809
01:04:35,559 --> 01:04:39,390
I mean you could put electrodes in that thing
and put an electrical rod in there and strike
810
01:04:39,390 --> 01:04:43,630
and arc and weld with them and break the arc,
strike and arc and weld and break the arc.
811
01:04:43,630 --> 01:04:45,839
And they just do it repeatedly.
812
01:04:45,839 --> 01:04:51,930
You can throw a switch, they are on, you throw
a switch and they are off.
813
01:04:51,930 --> 01:04:53,920
And so they are very, very simple.
814
01:04:53,920 --> 01:04:59,039
I really, really wanted us to go with an all
electrical system using electrical motors
815
01:04:59,039 --> 01:05:06,039
and power hinges and electrical mechanical
actuators to drive the systems because I was
816
01:05:08,950 --> 01:05:13,930
absolutely convinced that one of these days
we were going to have a leak in the hydraulic
817
01:05:13,930 --> 01:05:14,890
system.
818
01:05:14,890 --> 01:05:21,890
And when we have a leak in the hydraulic system
we are going to have a fire.
819
01:05:24,210 --> 01:05:25,920
All airplanes have hydraulic leaks.
820
01:05:25,920 --> 01:05:30,059
Now, you don't have to worry too much about
hydraulic leaks on an airplane.
821
01:05:30,059 --> 01:05:35,049
You have enough pressure where you seldom
have to worry about a fire.
822
01:05:35,049 --> 01:05:42,049
We went from 5606 hydraulic fluid to 83282
hydraulic fluid simply because it was advertised
823
01:05:44,799 --> 01:05:46,190
as being more flame-resistant.
824
01:05:46,190 --> 01:05:52,020
It is really not more flame-resistant.
825
01:05:52,020 --> 01:05:59,020
The 83282 hydraulic fluid has a much, much
lower vapor pressure than does 5606.
826
01:06:01,619 --> 01:06:05,490
And a way that they test it is they have got
a Bunsen burner out here.
827
01:06:05,490 --> 01:06:09,700
They take a pipe cleaner and dip it in the
fluid, clamp it in this device that rotates
828
01:06:09,700 --> 01:06:15,369
past that Bunsen burner and they count the
number of times it will go across it before
829
01:06:15,369 --> 01:06:17,140
the fire starts.
830
01:06:17,140 --> 01:06:23,210
Well, with 5606, it will usually start on
a third burn.
831
01:06:23,210 --> 01:06:30,210
With 83282 it takes 10, 11, 12 passes before
it will ignite and start burning simply because
832
01:06:32,289 --> 01:06:38,670
it has a lower vapor pressure and you cannot
burn any liquid in a liquid stage.
833
01:06:38,670 --> 01:06:42,940
You have to get it warm enough so that it
will gasify.
834
01:06:42,940 --> 01:06:47,530
And then you have to heat it enough in a gas
phase to get it up to the combustion temperature
835
01:06:47,530 --> 01:06:50,160
or put a spark in it after it is in the gas
phase.
836
01:06:50,160 --> 01:06:52,819
But it won't ignite as a liquid.
837
01:06:52,819 --> 01:06:59,440
Well, with 6506, if you have a leak in the
hydraulic system going uphill you probably
838
01:06:59,440 --> 01:07:01,869
don't have to worry about it coming home because
it's gone.
839
01:07:01,869 --> 01:07:06,440
It all boils off and is gone.
840
01:07:06,440 --> 01:07:12,510
With 83282 all it does is soak out into the
structure and in the insulation and all over
841
01:07:12,510 --> 01:07:12,890
the place.
842
01:07:12,890 --> 01:07:17,260
And then when you come back home, if it gets
in a hot spot and you start heating it up,
843
01:07:17,260 --> 01:07:23,380
it forms a gas and you're going to get an
explosion in the back of the vehicle.
844
01:07:23,380 --> 01:07:25,890
So, that was a bad decision, Aaron.
845
01:07:25,890 --> 01:07:32,890
We went in a bad direction, but it gave everybody
a warm feeling.
846
01:07:35,650 --> 01:07:42,650
We would have went with an electric mechanical
system but, by that time, we had a lot of
847
01:07:46,819 --> 01:07:49,510
hydraulic people working on the program.
848
01:07:49,510 --> 01:07:53,760
And we would lay those people all off and
we had our whole bunch of electrical mechanical
849
01:07:53,760 --> 01:07:57,799
people, and a lot of people were concerned
about the immaturity of those systems.
850
01:07:57,799 --> 01:08:02,119
And again it boiled down to development cost.
851
01:08:02,119 --> 01:08:04,920
Did we really have the energy source that
could handle that?
852
01:08:04,920 --> 01:08:09,750
Oh, I'm convinced that we could have put six
or eight of those fuel cells that we've got
853
01:08:09,750 --> 01:08:15,099
on there right now and could have handled
it.
854
01:08:15,099 --> 01:08:19,450
Broke it down.
855
01:08:19,450 --> 01:08:26,450
And the fuel cells that DOD had under development
at that time were very, very good fuel cells.
856
01:08:27,949 --> 01:08:33,150
If I was upgrading the shuttle today that
is one of the things that I absolutely would
857
01:08:33,150 --> 01:08:33,659
go to.
858
01:08:33,659 --> 01:08:37,850
I would go to something to get rid of the
hydraulic fluid.
859
01:08:37,850 --> 01:08:44,850
It creates a lot of other kinds of problems
that you have to deal with.
860
01:08:48,750 --> 01:08:54,330
Actually, before the decision was made that
the shuttle was going to be retired in five
861
01:08:54,330 --> 01:09:00,679
years, NASA was working on upgrades if we
were going to fly the shuttle for another
862
01:09:00,679 --> 01:09:02,679
20 or 25 years.
863
01:09:02,679 --> 01:09:08,500
And one of the upgrades, which actually got
to a fairly advanced stage in the design,
864
01:09:08,500 --> 01:09:10,460
was just what you were saying.
865
01:09:10,460 --> 01:09:17,460
Get rid of the APU/hydraulics, use the latest
technology now available for electromechanical
866
01:09:18,250 --> 01:09:19,060
actuators.
867
01:09:19,060 --> 01:09:24,420
But the problem, I don't know the details
of it, but the costs just kept going up and
868
01:09:24,420 --> 01:09:25,250
up and up.
869
01:09:25,250 --> 01:09:30,640
And by the time it went up above about $300
million they just said we cannot afford to
870
01:09:30,640 --> 01:09:32,259
do this.
871
01:09:32,259 --> 01:09:39,259
The problem we always had in trying to upgrade
the propulsion, we could have gone to an alcohol/LOX
872
01:09:40,029 --> 01:09:42,080
space RCS/OMS on it.
873
01:09:42,080 --> 01:09:48,210
We could have upgraded to an electromechanical
system, but it seemed to me like that the
874
01:09:48,210 --> 01:09:54,250
displays and those kinds of upgrades took
a lot of computers.
875
01:09:54,250 --> 01:10:01,250
Those systems took a lot of priority in where
the monies went in trying to upgrade the Orbiter.
876
01:10:11,280 --> 01:10:18,280
We did go from four to three systems.
877
01:10:19,090 --> 01:10:26,090
We did go from 4 APUs to 3 APUs and still
having the ability to land the vehicle with
878
01:10:30,230 --> 01:10:33,570
one APU.
879
01:10:33,570 --> 01:10:35,860
We look at hydrogen/oxygen APUs.
880
01:10:35,860 --> 01:10:40,159
We looked at bipropellant APUs.
881
01:10:40,159 --> 01:10:45,550
We looked at monopropellant APUs.
882
01:10:45,550 --> 01:10:49,570
We looked at pulse modulated versus pressure
modulated.
883
01:10:49,570 --> 01:10:54,460
If you don't know what I mean by that, pulse
modulated is when you have a valve that goes
884
01:10:54,460 --> 01:11:01,420
open and closed and you get steady state pressure
in your gas generator while it is on.
885
01:11:01,420 --> 01:11:06,090
Pressure modulated you have a throttle valve
where you throttle the flow down going to
886
01:11:06,090 --> 01:11:12,610
the gas generator to give you just the power
that you need for the load that you are trying
887
01:11:12,610 --> 01:11:15,520
to pull at the time.
888
01:11:15,520 --> 01:11:22,520
And that was the easiest system to come up
with simply because we did not know at the
889
01:11:24,929 --> 01:11:31,929
time if we could build a valve that was capable
of millions and millions of cycles and not
890
01:11:32,150 --> 01:11:34,080
a leak.
891
01:11:34,080 --> 01:11:39,540
But the problem with a pressure modulated
system was that most of the time you're operating
892
01:11:39,540 --> 01:11:42,730
at very, very low power levels.
893
01:11:42,730 --> 01:11:47,469
The power just peaks up every once in a while
to high power levels.
894
01:11:47,469 --> 01:11:53,420
But when you're running very low pressures
in a gas turbine, the turbine becomes less
895
01:11:53,420 --> 01:11:56,920
efficient.
896
01:11:56,920 --> 01:12:02,300
And the less efficient the turbine becomes
the more propellant you have to burn and,
897
01:12:02,300 --> 01:12:03,800
again, the weight goes up.
898
01:12:03,800 --> 01:12:10,800
So we kind of bit the bullet on that and went
to a pressure modulated system where we varied
899
01:12:12,719 --> 01:12:15,570
the ohm time.
900
01:12:15,570 --> 01:12:18,650
In valve development we were very successful.
901
01:12:18,650 --> 01:12:25,650
We had very little trouble getting a valve
that would work, except for contamination.
902
01:12:27,530 --> 01:12:29,310
We always had a little contamination.
903
01:12:29,310 --> 01:12:32,900
We had a lot of problems down the Cape with
early valves leaking.
904
01:12:32,900 --> 01:12:38,219
We finally put good filters in the system
and that eliminated that.
905
01:12:38,219 --> 01:12:38,469
Yes.
906
01:12:38,270 --> 01:12:45,270
Was the reason to go from four to three APUs
just a weight issue?
907
01:12:46,850 --> 01:12:50,409
It's again a weight issue.
908
01:12:50,409 --> 01:12:54,120
All of that weight was in the back of the
vehicle, and the back of the vehicle was always
909
01:12:54,120 --> 01:12:55,560
too heavy.
910
01:12:55,560 --> 01:12:59,090
And every time we could take a pound out of
the back of the vehicle, we could take a pound
911
01:12:59,090 --> 01:13:02,030
of ballast out of the front of the vehicle,
so there were two pounds you didn't have to
912
01:13:02,030 --> 01:13:03,010
carry.
913
01:13:03,010 --> 01:13:07,150
So, it was strictly weight.
914
01:13:07,150 --> 01:13:11,239
I'm sorry, the APUs are turbines?
915
01:13:11,239 --> 01:13:14,659
I mean you're combusting [UNINTELLIGIBLE]?
916
01:13:14,659 --> 01:13:21,659
The APUs we settled on was going with a monopropellant
hydrazine, feed that through a catalyst bed
917
01:13:23,330 --> 01:13:24,790
and then through a turbine.
918
01:13:24,790 --> 01:13:27,380
We looked at dual stage, triple stage turbines.
919
01:13:27,380 --> 01:13:33,610
We finally wound up with a single stage turbine
running at about 38,000 to 45,000, I don't
920
01:13:33,610 --> 01:13:35,170
remember the exact number now, RPM.
921
01:13:35,170 --> 01:13:36,590
About ten inches in diameter [UNINTELLIGIBLE].
922
01:13:36,590 --> 01:13:43,590
The gas went in and then made a pass and went
back through, so we got maybe 5%, 10% more
923
01:13:49,469 --> 01:13:52,840
power out of it the second time through, a
little bit more power out of it the second
924
01:13:52,840 --> 01:13:56,530
time through.
925
01:13:56,530 --> 01:14:03,530
When we contracted for the APU, the contractor
did not have altitude facilities.
926
01:14:05,159 --> 01:14:12,159
And so they proposed that we did not need
to test the APU in a vacuum because that was
927
01:14:12,820 --> 01:14:18,210
all structure and all they had to do was pull
a vacuum on the exhaust and could get the
928
01:14:18,210 --> 01:14:19,820
performance out of that.
929
01:14:19,820 --> 01:14:26,159
So we did not have it in our quality program
to test the APU in a vacuum.
930
01:14:26,159 --> 01:14:27,929
Fortunately, Dr.
931
01:14:27,929 --> 01:14:34,929
Cohen gave us enough money to buy an APU offline
of the Shuttle Program.
932
01:14:35,429 --> 01:14:37,030
We brought it down to JSC.
933
01:14:37,030 --> 01:14:40,580
We put it in our vacuum facilities there.
934
01:14:40,580 --> 01:14:46,690
And we programmed the vacuum facility to go
down in pressure.
935
01:14:46,690 --> 01:14:48,780
The Orbiter was going up in altitude.
936
01:14:48,780 --> 01:14:55,780
And we ran the ascent profile and shut the
APU off just like we would on a first flight.
937
01:14:56,900 --> 01:15:03,050
And five minutes after we shut it off it exploded,
it detonated.
938
01:15:03,050 --> 01:15:05,429
I mean talk about things coming unglued.
939
01:15:05,429 --> 01:15:06,520
Everything came unglued.
940
01:15:06,520 --> 01:15:10,380
Aaron came unglued.
941
01:15:10,380 --> 01:15:11,770
We got another APU.
942
01:15:11,770 --> 01:15:12,719
We brought it down there.
943
01:15:12,719 --> 01:15:16,199
We brought all of the contractor people down,
everybody down there.
944
01:15:16,199 --> 01:15:17,860
We repeated the test.
945
01:15:17,860 --> 01:15:19,730
It exploded again.
946
01:15:19,730 --> 01:15:24,070
[LAUGHTER] By that time we discovered what
the problem was.
947
01:15:24,070 --> 01:15:29,120
We have a requirement in the program that
you can only have hot surfaces up to about
948
01:15:29,120 --> 01:15:30,110
500 degrees.
949
01:15:30,110 --> 01:15:33,040
I don't remember the exact temperature, but
some temperature like 500 degrees.
950
01:15:33,040 --> 01:15:36,429
If it is higher than that you have to shield
it.
951
01:15:36,429 --> 01:15:43,429
The gas generator is obviously running over
500 degrees, probably up around 800, 900 degrees,
952
01:15:44,060 --> 01:15:45,790
so we put a heat shield around it.
953
01:15:45,790 --> 01:15:51,270
We covered that whole thing up and had about
a half-inch standoff in the insulation on
954
01:15:51,270 --> 01:15:51,969
that thing.
955
01:15:51,969 --> 01:15:58,440
When you run it in one atmosphere, if you
shut it off it acts like a chimney.
956
01:15:58,440 --> 01:16:02,969
The air heats up between the insulation and
the hot surface and goes out the top.
957
01:16:02,969 --> 01:16:04,690
It draws cold air in.
958
01:16:04,690 --> 01:16:05,710
It goes out the top.
959
01:16:05,710 --> 01:16:09,570
It draws more cold air in so it cools it off.
960
01:16:09,570 --> 01:16:14,540
So the heat never did soak out into the valves
and get the valves too hot.
961
01:16:14,540 --> 01:16:19,580
When you put it in a vacuum there is no place
for that heat to go.
962
01:16:19,580 --> 01:16:23,420
And so all of that heat that was in the gas
generator and all of the catalyst and all
963
01:16:23,420 --> 01:16:28,730
of that soaked back out through the structure
and through the tubes back up to the valves
964
01:16:28,730 --> 01:16:32,940
and got the valves up to the temperature at
which hydrazine will detonate.
965
01:16:32,940 --> 01:16:35,659
And it did.
966
01:16:35,659 --> 01:16:38,280
It is so simple.
967
01:16:38,280 --> 01:16:41,710
It is so easy to understand after you know
about it.
968
01:16:41,710 --> 01:16:45,530
But to think about it, I remember sitting
around there one night to 8:00, 9:00 with
969
01:16:45,530 --> 01:16:51,150
all of my troops discussing the pros and cons
of an altitude facility.
970
01:16:51,150 --> 01:16:52,420
Do we have to have it?
971
01:16:52,420 --> 01:16:56,010
Do we have to direct the contractor to put
one in?
972
01:16:56,010 --> 01:17:03,010
And we could not come up with a good reason
to put an altitude test in the program so
973
01:17:03,210 --> 01:17:05,400
we didn't put it in there.
974
01:17:05,400 --> 01:17:11,570
Fortunately, just like on ohms with the helium
bottle falling out, we had a backup because
975
01:17:11,570 --> 01:17:17,800
some of the people weren't confident in flying
the vehicle without that test.
976
01:17:17,800 --> 01:17:20,300
And we found something that we didn't expect.
977
01:17:20,300 --> 01:17:23,940
The message that Henry is giving you on testing
is the same message that J.R.
978
01:17:23,940 --> 01:17:27,010
Thompson gave you on testing on the main engine.
979
01:17:27,010 --> 01:17:31,480
And, in contrast, we didn't really do that
type of testing on the solid rocket booster,
980
01:17:31,480 --> 01:17:33,409
the fair we had and on the foam.
981
01:17:33,409 --> 01:17:35,520
And that is the difference, we really tested.
982
01:17:35,520 --> 01:17:38,460
When we saw a problem we tested it.
983
01:17:38,460 --> 01:17:45,460
And we came out very fortunate, but we did
do it.
984
01:17:47,040 --> 01:17:52,530
Another thing with the development of the
APU, we flew those things on airplanes all
985
01:17:52,530 --> 01:17:59,530
the time in case they lost main engine, our
fighter aircraft and then some of the other
986
01:18:02,590 --> 01:18:05,340
airplanes including that supersonic plane
that we had.
987
01:18:05,340 --> 01:18:11,920
It had APUs in there in case they lost engine
power to provide hydraulics to be able to
988
01:18:11,920 --> 01:18:12,880
land the vehicle.
989
01:18:12,880 --> 01:18:19,880
And that got a lot of the flack because the
Aerospace Safety Committee told me that those
990
01:18:20,429 --> 01:18:23,210
systems never did work because they're called
auxiliary power units.
991
01:18:23,210 --> 01:18:26,239
They never worked when you needed them.
992
01:18:26,239 --> 01:18:29,860
But they had those systems.
993
01:18:29,860 --> 01:18:31,570
And they were good systems.
994
01:18:31,570 --> 01:18:38,570
But when we tried to use that same kind of
design on the Shuttle the oil wouldn't go
995
01:18:38,980 --> 01:18:43,260
back to the sump in the absence of gravity.
996
01:18:43,260 --> 01:18:46,159
You sling it out and it just coats the walls
on an automobile.
997
01:18:46,159 --> 01:18:51,670
You put an oil pan down the bottom, you put
a pump right at the bottom, you put a little
998
01:18:51,670 --> 01:18:55,360
filter in there and pump the oil out and pump
it through the engine and use it over and
999
01:18:55,360 --> 01:18:56,469
over and over.
1000
01:18:56,469 --> 01:19:00,850
But when you have no bottom, you have no place
for that oil to go.
1001
01:19:00,850 --> 01:19:06,989
So we had to come up with a technique where
we could use the gears as oil pumps.
1002
01:19:06,989 --> 01:19:13,989
And we came up with very, very close tolerances
between the gear and the case, and let the
1003
01:19:14,040 --> 01:19:19,340
gear sling the oil out or pump the oil out
into a cavity and pipe it off to where we
1004
01:19:19,340 --> 01:19:26,340
had a sump to where we could pick oil up with
an oil pump and pump it back through the system.
1005
01:19:26,840 --> 01:19:32,210
And we had some problems with some hydrazine
getting in there and gelling it one time.
1006
01:19:32,210 --> 01:19:37,560
And Fram came out with this deal where you
could pay me now or you can pay me later kind
1007
01:19:37,560 --> 01:19:43,610
of thing because they still aren't changing
the oil filter.
1008
01:19:43,610 --> 01:19:50,210
Hydraulics was mostly off the shelf at the
time, the pump and that stuff.
1009
01:19:50,210 --> 01:19:55,190
We did go to titanium propellant lines or
hydraulic lines.
1010
01:19:55,190 --> 01:20:01,440
We did develop a special fitting to put titanium
lines together.
1011
01:20:01,440 --> 01:20:05,900
It turned out to be very, very good.
1012
01:20:05,900 --> 01:20:12,510
We did have to add a water boiler to cool
the hydraulic fluid because on airplanes just
1013
01:20:12,510 --> 01:20:16,800
put a little radiator in there and use the
atmosphere to cool it, but that didn't work
1014
01:20:16,800 --> 01:20:18,940
in space.
1015
01:20:18,940 --> 01:20:25,940
The first one they came up with was a bucket
and it had a core of tubes in that bucket
1016
01:20:26,780 --> 01:20:32,179
with a pipe that went out with some baffles
in there to keep the liquid from going out.
1017
01:20:32,179 --> 01:20:37,030
But there, again, they did not understand
the absence of gravity.
1018
01:20:37,030 --> 01:20:43,400
When in zero G and you put heat in that water,
it just pushes the water out away from the
1019
01:20:43,400 --> 01:20:44,870
tube.
1020
01:20:44,870 --> 01:20:49,460
And all the water would go out the exhaust
pipe and you would have nothing but gas in
1021
01:20:49,460 --> 01:20:50,380
the tank.
1022
01:20:50,380 --> 01:20:54,590
We had to change that design and go into what
we call a water spray barge.
1023
01:20:54,590 --> 01:21:01,590
To pulse the water in there as a spray is
more efficient.
1024
01:21:03,360 --> 01:21:10,360
But complicated that system very much.
1025
01:21:10,889 --> 01:21:14,260
It still does.
1026
01:21:14,260 --> 01:21:21,260
It is very, very difficult to handle water
in a vacuum.
1027
01:21:23,380 --> 01:21:28,949
Getting back to the RCS one moment, the first
rain we had down there at the Cape, the RCS
1028
01:21:28,949 --> 01:21:30,780
jets filled up with water.
1029
01:21:30,780 --> 01:21:37,780
And they wanted to launch that system assuming
that the water would boil out when they started
1030
01:21:38,090 --> 01:21:38,850
going uphill.
1031
01:21:38,850 --> 01:21:45,510
But, no, what happens is when you put water
in a vacuum, about 60% of it will go to a
1032
01:21:45,510 --> 01:21:47,949
gas and 30% will freeze.
1033
01:21:47,949 --> 01:21:52,429
When it freezes then it is a solid, you cannot
get it out, it just has to sublime which takes
1034
01:21:52,429 --> 01:21:54,010
weeks and months.
1035
01:21:54,010 --> 01:22:00,620
Now, trying to get us a water boiler, we had
valves in there that were supposed to open
1036
01:22:00,620 --> 01:22:03,880
and close when the pressure built up.
1037
01:22:03,880 --> 01:22:10,880
Well, when you get past that valve, when that
valve would open up that steam would instantly
1038
01:22:12,040 --> 01:22:16,340
freeze on the outside and it keeps growing
back.
1039
01:22:16,340 --> 01:22:21,179
Finally, the valve would be stopped up and
you would build the pressure up way high and
1040
01:22:21,179 --> 01:22:22,150
would blow the ice out.
1041
01:22:22,150 --> 01:22:25,360
The pressure would come back down and start
working again.
1042
01:22:25,360 --> 01:22:27,469
So, we went to an orifice.
1043
01:22:27,469 --> 01:22:34,469
Trying to size that orifice to the right size
where it maintains a little pressure in there,
1044
01:22:34,719 --> 01:22:39,790
and you've got a variable load on the system
and you're putting variable energy into it,
1045
01:22:39,790 --> 01:22:41,630
that's difficult to design that, too.
1046
01:22:41,630 --> 01:22:43,440
The water boiler still freezes.
1047
01:22:43,440 --> 01:22:45,110
We still have a freezing problem on it.
1048
01:22:45,110 --> 01:22:51,380
It is not an easy solution to it.
1049
01:22:51,380 --> 01:22:55,610
Questions?
1050
01:22:55,610 --> 01:23:00,489
Do you lose that water?
1051
01:23:00,489 --> 01:23:04,670
Yeah, we just dump it overboard.
1052
01:23:04,670 --> 01:23:09,510
We have a whole bunch of tubes going through
this water, and we spray the water in, in
1053
01:23:09,510 --> 01:23:09,810
a spray.
1054
01:23:09,810 --> 01:23:16,810
And it makes one pass through those tubes
and then it goes out the exhaust.
1055
01:23:17,420 --> 01:23:22,480
If you wanted to come up with some kind of
regenerative system where you would use the
1056
01:23:22,480 --> 01:23:26,730
water over and over and over then you've got
to go through some kind of system to cool
1057
01:23:26,730 --> 01:23:30,130
the water or you have to carry too much water
aboard.
1058
01:23:30,130 --> 01:23:35,440
Well, if you want to cool the water, the only
way you really have got to cool it is by using
1059
01:23:35,440 --> 01:23:42,440
more water or supplementing some of that water.
1060
01:23:42,949 --> 01:23:49,949
In a vacuum, you cannot just put it out on
a surface some place.
1061
01:23:50,159 --> 01:23:52,159
I guess the temperature varies maybe.
1062
01:23:52,159 --> 01:23:59,159
Henry, could you say a word about the flight
control hydraulics lab, the tests we ran with
1063
01:23:59,650 --> 01:24:02,440
the hydraulic systems.
1064
01:24:02,440 --> 01:24:07,340
The hydraulic system was probably one of the
most thoroughly tested systems that we had
1065
01:24:07,340 --> 01:24:12,860
as far as mechanical systems were concerned.
1066
01:24:12,860 --> 01:24:19,820
We built a whole hydraulic system integrated
with the avionics, and we had it designed
1067
01:24:19,820 --> 01:24:23,610
so you could put loads on it and react the
loads.
1068
01:24:23,610 --> 01:24:28,090
And you could program in what you thought
was typical emissions where you could vary
1069
01:24:28,090 --> 01:24:29,090
everything.
1070
01:24:29,090 --> 01:24:34,739
The only difference is instead of driving
the hydraulic pumps with APUs, we drove the
1071
01:24:34,739 --> 01:24:41,739
hydraulic pumps with electric motors because
we had ground-based electric motors to drive
1072
01:24:41,739 --> 01:24:43,280
them.
1073
01:24:43,280 --> 01:24:50,280
And one of the things we ground ruled out
was the use of flex hoses -belts- simply because
1074
01:24:51,449 --> 01:24:58,280
they, at that time, were notorious for fatiguing
and breaking and not working very good.
1075
01:24:58,280 --> 01:25:01,150
So we put trombone tubes in.
1076
01:25:01,150 --> 01:25:05,760
Take a long tube and bring it back this way
and tie it in.
1077
01:25:05,760 --> 01:25:09,670
And now, as the actuator moved, it could move.
1078
01:25:09,670 --> 01:25:13,920
And you had enough spring or enough give in
those tubes.
1079
01:25:13,920 --> 01:25:18,710
On the very first time they fired that thing
up, standing up in there in the control room
1080
01:25:18,710 --> 01:25:22,650
looking at it, those trombone tubes just vanished.
1081
01:25:22,650 --> 01:25:29,449
They would be there and then all at once you
wouldn't see them.
1082
01:25:29,449 --> 01:25:31,030
And I mean you couldn't see them.
1083
01:25:31,030 --> 01:25:34,190
You're standing up there in the control room
looking and there are no tubes in there.
1084
01:25:34,190 --> 01:25:36,679
They were shaking so bad that you couldn't
see them.
1085
01:25:36,679 --> 01:25:43,310
So we went through a big effort to figure
out ways to damp those things and isolate
1086
01:25:43,310 --> 01:25:49,420
them so that they didn't vibrate.
1087
01:25:49,420 --> 01:25:51,780
We had a major failure.
1088
01:25:51,780 --> 01:25:58,699
It was a hard, hard sell to convince the people
to go to a single actuary, from a dual tandem
1089
01:25:58,699 --> 01:26:00,150
single actuator.
1090
01:26:00,150 --> 01:26:07,150
Well, no more than we got our first single
actuator built, the initial design had too
1091
01:26:09,710 --> 01:26:13,440
much slack in a tube that went from one side
to the other side because you had to have
1092
01:26:13,440 --> 01:26:14,900
an expansion joint in there.
1093
01:26:14,900 --> 01:26:16,949
And we had an O ring in there.
1094
01:26:16,949 --> 01:26:22,340
And they had too much slack in there and it
blew one of the O rings out.
1095
01:26:22,340 --> 01:26:26,070
Well, of course, when you blew an O ring out
you lost all the hydraulics not only from
1096
01:26:26,070 --> 01:26:31,400
that system but all three systems because
it was downstream of the switching valves.
1097
01:26:31,400 --> 01:26:34,940
And when one system ran out of fluid it would
switch over to the other one and you would
1098
01:26:34,940 --> 01:26:40,300
run out of fluid.
1099
01:26:40,300 --> 01:26:46,270
Had we not had a very, very strong guy in
the Program Office at that time that never
1100
01:26:46,270 --> 01:26:51,570
gave up on anything that would have probably
finished us off as far as single actuators
1101
01:26:51,570 --> 01:26:53,050
are concerned.
1102
01:26:53,050 --> 01:26:59,090
But we were able to convince the program that
if we tightened the tolerance up on it, paid
1103
01:26:59,090 --> 01:27:03,630
very close attention to the tolerance on it
that it could not happen.
1104
01:27:03,630 --> 01:27:05,630
And it has not happened again.
1105
01:27:05,630 --> 01:27:06,889
Another question?
1106
01:27:06,889 --> 01:27:07,520
Yes.
1107
01:27:07,520 --> 01:27:13,560
You talked a little bit before about maybe
substituting an electromechanical system for
1108
01:27:13,560 --> 01:27:14,030
hydraulic.
1109
01:27:14,030 --> 01:27:21,030
Would there be any other changes you would
make in the design if you had to go back and
1110
01:27:22,580 --> 01:27:24,040
do it again?
1111
01:27:24,040 --> 01:27:27,870
Oh, if I had to do it again, I definitely
would go with electromechanical systems.
1112
01:27:27,870 --> 01:27:30,590
Now, that takes on many varieties.
1113
01:27:30,590 --> 01:27:37,540
You could have small electric motors driving
a hydraulic system right at the unit.
1114
01:27:37,540 --> 01:27:40,469
Like you put an electric motor on an actuator.
1115
01:27:40,469 --> 01:27:46,120
And that electric motor drives a small hydraulic
pump that would move the actuator if you did
1116
01:27:46,120 --> 01:27:53,120
not have confidence in worm gears and screw
jacks and those kind of things to provide
1117
01:27:59,330 --> 01:28:03,699
the mechanical force, power hinges and things
like that.
1118
01:28:03,699 --> 01:28:08,010
But there is absolutely no question in my
mind that one of the safest things you could
1119
01:28:08,010 --> 01:28:15,010
do for the Orbiter right now would be to replace
the APUs in the hydraulic system with an electrical
1120
01:28:21,060 --> 01:28:23,460
system.
1121
01:28:23,460 --> 01:28:30,460
We have the motor technology, we have, I think,
the gear and the ball screw technology to
1122
01:28:31,510 --> 01:28:33,010
be able to do that.
1123
01:28:33,010 --> 01:28:36,719
I think we could do it cheap.
1124
01:28:36,719 --> 01:28:40,469
I think that would really change the operational
cost.
1125
01:28:40,469 --> 01:28:44,420
It would reduce the operational of cost immensely.
1126
01:28:44,420 --> 01:28:49,400
It would move the CG further forward on the
vehicle so you probably could take out a little
1127
01:28:49,400 --> 01:28:52,580
bit more of the ballast that we usually fly
on the front-end.
1128
01:28:52,580 --> 01:28:54,739
I guess we're still flying it.
1129
01:28:54,739 --> 01:28:58,130
We always did.
1130
01:28:58,130 --> 01:29:02,650
I have another question.
1131
01:29:02,650 --> 01:29:08,340
You talked earlier and you had it on the slide,
but you didn't really talk about it, how you
1132
01:29:08,340 --> 01:29:12,090
were shifting weight between budgets, when
it came to like the controls people versus
1133
01:29:12,090 --> 01:29:14,139
the hydraulics people and the APUs.
1134
01:29:14,139 --> 01:29:19,330
And I was wondering if you could kind of just
expand on that of how, in an actual development
1135
01:29:19,330 --> 01:29:20,739
program, it goes back and forth.
1136
01:29:20,739 --> 01:29:24,880
I mean does it usually come down from high
you're going to do this and you're going to
1137
01:29:24,880 --> 01:29:28,469
do that, or is it usually they let you kind
of work it out between the groups or what?
1138
01:29:28,469 --> 01:29:31,050
The control people have no weight budget.
1139
01:29:31,050 --> 01:29:38,050
I mean their budget is the electrons that
flow back and forth and the requirements.
1140
01:29:39,600 --> 01:29:44,469
What they do is they start out a requirement
that they would like to have.
1141
01:29:44,469 --> 01:29:51,469
And it is usually two, three, four times what
they absolutely have to have.
1142
01:29:52,219 --> 01:29:57,570
And then you have to sit down and start negotiating
with them and explaining to them what it is
1143
01:29:57,570 --> 01:29:57,980
costing.
1144
01:29:57,980 --> 01:30:02,840
And often it gets down to the fact that the
vehicle won't fly.
1145
01:30:02,840 --> 01:30:05,139
I mean it just flat won't fly.
1146
01:30:05,139 --> 01:30:09,420
And when they are convinced then that it cannot
fly then they are willing to concede that
1147
01:30:09,420 --> 01:30:12,100
they can get by with a little more.
1148
01:30:12,100 --> 01:30:15,510
And it still won't fly and so they can get
by with a little bit more.
1149
01:30:15,510 --> 01:30:20,880
And that's kind of the way you get it done.
1150
01:30:20,880 --> 01:30:26,590
That's what you do.
1151
01:30:26,590 --> 01:30:30,860
You have a work breakdown structure, and you
parcel that work breakdown structure out to
1152
01:30:30,860 --> 01:30:32,659
your subsystem managers.
1153
01:30:32,659 --> 01:30:36,909
Now, there was an issue in the Shuttle and
the Apollo Program, since I was a project
1154
01:30:36,909 --> 01:30:43,909
manager, you give the subsystem managers the
requirements and the authority technically.
1155
01:30:44,389 --> 01:30:51,389
You tell them what their constraint is for
dollars, you give them the weight bogies or
1156
01:30:52,090 --> 01:30:57,520
the weight requirements, the function requirements,
performance requirements, the schedule requirements,
1157
01:30:57,520 --> 01:30:58,400
but you keep the dollars.
1158
01:30:58,400 --> 01:31:00,530
Now, that's been a very long argument.
1159
01:31:00,530 --> 01:31:05,469
Do you allow the subsystem managers to actually
have control over the dollars?
1160
01:31:05,469 --> 01:31:06,600
We decided not to.
1161
01:31:06,600 --> 01:31:11,199
That was a very big argument of whether you
should let the other people have the dollars.
1162
01:31:11,199 --> 01:31:14,170
I kept the dollars.
1163
01:31:14,170 --> 01:31:18,350
They had to come to me if they wanted to make
a big change outside their work breakdown
1164
01:31:18,350 --> 01:31:24,360
structure because I had the problem of trading
off the dollars between the propulsion system
1165
01:31:24,360 --> 01:31:29,179
and the structure system or the aerodynamic
system.
1166
01:31:29,179 --> 01:31:32,260
And you can argue that was the right or wrong
thing to do but that was how we did it.
1167
01:31:32,260 --> 01:31:37,040
And I am not sure if aircraft companies like
Boeing now or Lockheed Martin how they do
1168
01:31:37,040 --> 01:31:41,670
it, but they all start off with a work breakdown
structure of some type.
1169
01:31:41,670 --> 01:31:42,389
Yes.
1170
01:31:42,389 --> 01:31:47,199
At that stage,do you also give them target
weights?
1171
01:31:47,199 --> 01:31:48,960
You can target weights also, yeah.
1172
01:31:48,960 --> 01:31:50,250
Negotiated target weights and negotiated schedules.
1173
01:31:50,250 --> 01:31:53,489
And they develop the performance.
1174
01:31:53,489 --> 01:31:59,830
You basically use the target weights, from
the preliminary designs that you've done,
1175
01:31:59,830 --> 01:32:04,850
to look at the concept that you're looking
at to make sure that it is feasible.
1176
01:32:04,850 --> 01:32:08,909
And when it looks like that is a feasible
design, then you break up the weights and
1177
01:32:08,909 --> 01:32:14,949
you give all of the subsystem people their
target weights to stay within of which almost
1178
01:32:14,949 --> 01:32:18,520
immediately the weights start growing.
1179
01:32:18,520 --> 01:32:19,389
That's right.
1180
01:32:19,389 --> 01:32:23,520
And, when you're a project manager like I
was, it is career limiting.
1181
01:32:23,520 --> 01:32:26,610
The first thing is your weight starts to go
up.
1182
01:32:26,610 --> 01:32:32,489
The next thing is you start to have schedule
slips because you're finding technology problems.
1183
01:32:32,489 --> 01:32:34,760
And then the cost starts to go up.
1184
01:32:34,760 --> 01:32:41,760
You really come with a lot of career limiting
problems in project managing, but you have
1185
01:32:44,550 --> 01:32:46,020
to have good people working for you.
1186
01:32:46,020 --> 01:32:50,320
I think, Henry, another interesting thing
you might talk about is, they've seen Bass
1187
01:32:50,320 --> 01:32:54,020
Redd talk about the aerodynamics, they are
going to have Phil Hattis talk about the guidance,
1188
01:32:54,020 --> 01:32:58,550
navigation and control, you might give them
your perspective with the hydraulic system
1189
01:32:58,550 --> 01:33:00,420
of tying those systems together.
1190
01:33:00,420 --> 01:33:07,420
You mentioned it a little bit but it is probably
a little bit harder than you think in putting
1191
01:33:09,889 --> 01:33:12,909
the requirements on the hydraulic system.
1192
01:33:12,909 --> 01:33:19,909
I probably spent more personal time dealing
with the avionics people, the guidance people
1193
01:33:22,659 --> 01:33:29,659
and the aero people than I did working with
the subsystem designs early on just trying
1194
01:33:32,520 --> 01:33:37,420
to get some reasonableness in the requirements.
1195
01:33:37,420 --> 01:33:42,980
Trying to get the size of the OMS engines
down, trying to get the size of the RCS down,
1196
01:33:42,980 --> 01:33:45,580
trying to get the pulse width a little bit
wider.
1197
01:33:45,580 --> 01:33:51,150
On the hydraulics, that was a major, major
issue because those were really big weight
1198
01:33:51,150 --> 01:33:53,550
items.
1199
01:33:53,550 --> 01:34:00,550
On the OMS and RCS it was not a big weight
impact, it was a performance impact of how
1200
01:34:00,750 --> 01:34:03,699
much propellants you had to carry onboard.
1201
01:34:03,699 --> 01:34:10,620
But on the hydraulics, on the design of that
system, how fast you had to move one of those
1202
01:34:10,620 --> 01:34:13,350
flaps on that thing was a big big issue.
1203
01:34:13,350 --> 01:34:18,300
And I spent lots of time going over and looking
at their data, looking at what they were coming
1204
01:34:18,300 --> 01:34:22,100
up with, looking at their what-ifs.
1205
01:34:22,100 --> 01:34:28,550
That is what drives a system, is what if this
happens or what if that happens?
1206
01:34:28,550 --> 01:34:32,110
Another problem I remember we had was the
gimbal rate of the main engines.
1207
01:34:32,110 --> 01:34:36,090
The requirement they put on the gimbal rate.
1208
01:34:36,090 --> 01:34:40,469
That was a compounded problem, too, because
you were kind of dealing between centers.
1209
01:34:40,469 --> 01:34:45,699
But, yeah, the gimbal weight.
1210
01:34:45,699 --> 01:34:52,000
And the need for a gimbal system on the solid
rocket motors, if I had my day in court, we
1211
01:34:52,000 --> 01:34:58,210
would take the gimbal system off of the solid
rocket boosters.
1212
01:34:58,210 --> 01:35:03,520
That would save six or seven or eight tons
of weight back there.
1213
01:35:03,520 --> 01:35:10,520
If you would take that system out, it would
make the solid rocket boosters much more reliable
1214
01:35:11,070 --> 01:35:14,800
because they've got those great big old boots
in there and those big springs.
1215
01:35:14,800 --> 01:35:19,909
They horse those things back and forth with
huge actuators on them.
1216
01:35:19,909 --> 01:35:26,909
And the only reason we could not eliminate
the gimbal system on the SRBs is that we had
1217
01:35:30,980 --> 01:35:36,340
one SRB that burned out with the max burn
time.
1218
01:35:36,340 --> 01:35:39,770
And the other one on the other side burned
out with minimum burn time.
1219
01:35:39,770 --> 01:35:44,690
And we lost the top engine on the SSME on
the same flight.
1220
01:35:44,690 --> 01:35:49,199
Now, you know the probability of that happening
is once in a billion.
1221
01:35:49,199 --> 01:35:55,130
But, yet, that is what drives the requirement
for having the gimbal system.
1222
01:35:55,130 --> 01:36:02,130
We would have to gimbal the main engines another
two degrees to make that work.
1223
01:36:02,369 --> 01:36:09,369
But that is what drove the design, that requirement
that we have on the solid rocket motors.
1224
01:36:09,489 --> 01:36:15,480
So, if I can leave you with one message, it
is understand your requirements extremely
1225
01:36:15,480 --> 01:36:22,480
well and understand the impact that that requirement
is having on your system and on the flyability
1226
01:36:25,639 --> 01:36:28,179
of the vehicle.
1227
01:36:28,179 --> 01:36:35,179
I told you that Henry had a lot of innovative
design.
1228
01:36:37,380 --> 01:36:38,690
Talk a little bit more about the RCS.
1229
01:36:38,690 --> 01:36:40,050
I thought you were going to mention that before.
1230
01:36:40,050 --> 01:36:43,530
When they got water and how you solved that
problem.
1231
01:36:43,530 --> 01:36:50,530
This is Henry Pohl's solution to a very complex
problem on the RCS system, on the pad.
1232
01:36:50,699 --> 01:36:57,560
When we got the RCS engines filled up with
water we needed to come up with a design to
1233
01:36:57,560 --> 01:37:03,449
keep the water out of the engines in case
of rain because it always rains at the Cape.
1234
01:37:03,449 --> 01:37:10,449
So that requirement fell on the contractor
to design a system to keep water from getting
1235
01:37:11,840 --> 01:37:13,389
into the RCS engines.
1236
01:37:13,389 --> 01:37:18,060
They came up with a plug with the throat and
another big seal to go around those big scarf
1237
01:37:18,060 --> 01:37:20,739
nozzles out there with an O ring on that.
1238
01:37:20,739 --> 01:37:22,540
And that was all tied together with cables.
1239
01:37:22,540 --> 01:37:25,610
And they stuck a big pole upside the vehicle.
1240
01:37:25,610 --> 01:37:32,010
And just before liftoff they were going to
pop that pole over and jerk all of that stuff
1241
01:37:32,010 --> 01:37:32,600
out.
1242
01:37:32,600 --> 01:37:36,580
And they were going to jerk it out fast enough
so that those big tanks would not fall down
1243
01:37:36,580 --> 01:37:38,780
and hit the tile and knock all the tile off.
1244
01:37:38,780 --> 01:37:44,600
Well, that looked kind of complex and complicated
to me.
1245
01:37:44,600 --> 01:37:50,860
We had a grocery store across the street by
the name of Wine Gardens, and I went down
1246
01:37:50,860 --> 01:37:57,860
and got a roll of that wrapping paper that
you use to wrap meats in that has wax on one
1247
01:38:01,560 --> 01:38:05,340
side and then paper on the other side.
1248
01:38:05,340 --> 01:38:11,010
I call it butcher paper, but butcher paper
is actually a little bit different.
1249
01:38:11,010 --> 01:38:17,699
If you go down and buy something it is freezer
paper, but I bought a roll of that.
1250
01:38:17,699 --> 01:38:22,560
Then I got back up into the meeting by the
time it was over and said this is the way
1251
01:38:22,560 --> 01:38:23,280
to fix it.
1252
01:38:23,280 --> 01:38:28,080
And I started tearing off sheets off and passed
it around to the managers to look at.
1253
01:38:28,080 --> 01:38:35,080
We are going to glue that on the surface with
the wax side out and glue it on with RTV.
1254
01:38:37,170 --> 01:38:39,780
And then, when you lift it off, it would come
off.
1255
01:38:39,780 --> 01:38:40,500
It was light.
1256
01:38:40,500 --> 01:38:41,989
It wouldn't hurt the tile.
1257
01:38:41,989 --> 01:38:43,510
If it impacted anything it wasn't going to
hurt anything.
1258
01:38:43,510 --> 01:38:49,469
If it didn't come off when you fired the RCS
you would blow it off or burn it off.
1259
01:38:49,469 --> 01:38:51,260
And that is what we did.
1260
01:38:51,260 --> 01:38:53,219
And we glued that on all of them.
1261
01:38:53,219 --> 01:38:57,310
[LAUGHTER] It sounds funny but it is true.
1262
01:38:57,310 --> 01:39:03,440
You look at the Orbiter sitting on the pad
and all the RCS jets are covered up with paper.
1263
01:39:03,440 --> 01:39:05,840
But after I left they changed that.
1264
01:39:05,840 --> 01:39:12,840
They changed from butcher paper to a special
paper developed special for that purpose that
1265
01:39:14,860 --> 01:39:17,400
is made out of Teflon.
1266
01:39:17,400 --> 01:39:23,730
You have to tell them one more story about
the SSME on the launch pad and the hydrogen.
1267
01:39:23,730 --> 01:39:25,940
This was JR's.
1268
01:39:25,940 --> 01:39:32,940
When we did the first firing on the pad -- Just
a test firing on the launch pad to make sure
1269
01:39:35,350 --> 01:39:40,530
that everything worked right, we blew the
back end out of the shuttle.
1270
01:39:40,530 --> 01:39:46,340
When those main engines light off, each one
of those engines dump out about 125 pounds
1271
01:39:46,340 --> 01:39:50,219
of hydrogen before it ignites.
1272
01:39:50,219 --> 01:39:52,610
That hydrogen is cold.
1273
01:39:52,610 --> 01:39:55,159
It is fairly dense in liquid form.
1274
01:39:55,159 --> 01:39:57,030
It is 4.5 pounds per cubic foot or something.
1275
01:39:57,030 --> 01:39:58,969
By that time it is a little bit lighter.
1276
01:39:58,969 --> 01:40:01,360
It goes down in the flame pit.
1277
01:40:01,360 --> 01:40:03,929
It mixes with a lot of air in there.
1278
01:40:03,929 --> 01:40:05,730
And then the flame hits it and detonates.
1279
01:40:05,730 --> 01:40:12,730
And it blew the backend out of the vehicle.
1280
01:40:12,810 --> 01:40:18,260
We needed a quick fix because we're going
to launch that thing in three or four days.
1281
01:40:18,260 --> 01:40:24,429
I looked at the problem and said we will just
put Roman candles under it.
1282
01:40:24,429 --> 01:40:29,489
You put a bunch of Roman candles under there
that fire those balls out across there and
1283
01:40:29,489 --> 01:40:30,560
the hydrogen comes out.
1284
01:40:30,560 --> 01:40:32,030
That will ignite the hydrogen.
1285
01:40:32,030 --> 01:40:34,480
It will burn and won't accumulate behind the
pit.
1286
01:40:34,480 --> 01:40:36,239
And that is what we did.
1287
01:40:36,239 --> 01:40:43,239
Those sparklers you see coming on before the
main engines light off, those are my Roman
1288
01:40:43,449 --> 01:40:43,730
candles.
1289
01:40:43,730 --> 01:40:47,239
And as long as we're talking about blowing
the back end of the Orbiter out, maybe you
1290
01:40:47,239 --> 01:40:54,239
can talk about the pressure wave as well.
1291
01:40:55,300 --> 01:41:01,380
The pressure wave that came back and the water
suppression.
1292
01:41:01,380 --> 01:41:06,639
We had another problem, more of an acoustical
problem from the pressure waves coming back
1293
01:41:06,639 --> 01:41:13,260
up under the Orbiter, and we needed some kind
of a solution to do that.
1294
01:41:13,260 --> 01:41:19,050
Back while I was in Huntsville as a test engineer
in a test lab there in Huntsville, we blew
1295
01:41:19,050 --> 01:41:25,760
the windows out seven miles away when we started
firing the Saturn 5 vehicle.
1296
01:41:25,760 --> 01:41:32,760
We spent a lot of time on sound suppression
techniques to reduce the pressure effect.
1297
01:41:37,949 --> 01:41:41,830
And one of the things we came up with is we
found water is very good at damping that.
1298
01:41:41,830 --> 01:41:47,440
When we had that problem down the Cape what
we did is put those sausages, the hammocks
1299
01:41:47,440 --> 01:41:54,270
across down there and fill them with water
to damp out the pressure wave that came back
1300
01:41:54,270 --> 01:41:55,800
up to the back of the vehicle.
1301
01:41:55,800 --> 01:41:58,530
There is another one of them.
1302
01:41:58,530 --> 01:42:01,760
Essentially like big water balloons.
1303
01:42:01,760 --> 01:42:04,159
We called them sausage.
1304
01:42:04,159 --> 01:42:09,699
It was a fabric across the bottom, filled
it up with water and it was strong enough
1305
01:42:09,699 --> 01:42:11,400
to hold the water up.
1306
01:42:11,400 --> 01:42:18,400
And then that dampened the sound waves, the
shockwaves that came back up through the vehicle.
1307
01:42:21,719 --> 01:42:28,719
Again, just remember that it is not natural
for earth-bound humans to think in terms of
1308
01:42:36,010 --> 01:42:40,219
the absence of gravity and the absence of
pressure.
1309
01:42:40,219 --> 01:42:44,550
I cannot stress that too much.
1310
01:42:44,550 --> 01:42:48,699
You take a pot of water, you put it on the
stove and it gets hot on top.
1311
01:42:48,699 --> 01:42:52,320
You put it on a stove at zero G, it does not
get hot on top.
1312
01:42:52,320 --> 01:42:55,540
It pushes all the water out.
1313
01:42:55,540 --> 01:42:56,260
Heat transfer.
1314
01:42:56,260 --> 01:42:59,960
You don't realize how much heat is transferred
out through the atmosphere.
1315
01:42:59,960 --> 01:43:05,350
If you have no atmosphere you don't get any
of that heat transfer out.
1316
01:43:05,350 --> 01:43:12,350
The other thing to remember is that there
is absolutely no substitute for a very well
1317
01:43:14,020 --> 01:43:17,400
thought out test program.
1318
01:43:17,400 --> 01:43:20,889
It is not easy to test in the absence of gravity.
1319
01:43:20,889 --> 01:43:27,510
It is not easy to test in the absence of pressure
when you are reducing large quantities of
1320
01:43:27,510 --> 01:43:29,080
gas or chemicals.
1321
01:43:29,080 --> 01:43:31,760
But that is very, very important.
1322
01:43:31,760 --> 01:43:38,760
And that is the one thing that really separates
a space program from anything that we do here
1323
01:43:40,690 --> 01:43:47,690
on earth, is that you have no atmosphere and
you have no gravity to help you in your design.
1324
01:43:48,510 --> 01:43:55,510
Yet, all of our thought process is based on
having gravity and having an atmosphere.
1325
01:43:57,440 --> 01:44:04,440
And some of the designs of various experiments
that I've worked with on Spacelab flights
1326
01:44:06,980 --> 01:44:07,230
and other flights, numerous failures.
1327
01:44:06,980 --> 01:44:13,980
And over half of the equipment that failed,
this is stuff generally that we use inside
1328
01:44:17,030 --> 01:44:24,030
the shuttle, it was because of thermal problems
that they would overheat just because people
1329
01:44:24,179 --> 01:44:26,239
didn't get the calculations right.
1330
01:44:26,239 --> 01:44:27,679
You have no convection.
1331
01:44:27,679 --> 01:44:34,679
And getting the thermal design to work is
just really difficult.
1332
01:44:35,440 --> 01:44:42,440
Convection is one of the major problems that
is overlooked because when you put heat in
1333
01:44:43,369 --> 01:44:46,440
one place on the ground it goes up.
1334
01:44:46,440 --> 01:44:51,480
If you take the gravity away it will not go
up.
1335
01:44:51,480 --> 01:44:56,580
And that changes the whole complex, the thermal
matrix.
1336
01:44:56,580 --> 01:45:03,110
Henry talked a little bit about the screen
system that was developed for the OMS and
1337
01:45:03,110 --> 01:45:10,110
RCS tanks, but just to make sure you appreciate
the complexity of this, you've probably seen
1338
01:45:12,010 --> 01:45:17,460
pictures of astronauts playing with food and
liquid, you blow these big liquid bubbles
1339
01:45:17,460 --> 01:45:19,239
and they just sort of float there.
1340
01:45:19,239 --> 01:45:22,500
Well, the liquid does the same thing inside
a fuel tank.
1341
01:45:22,500 --> 01:45:25,989
And when you push the button because you want
to turn your engine to turn on, how do you
1342
01:45:25,989 --> 01:45:32,989
get the fuel to flow into the engine?
1343
01:45:35,619 --> 01:45:38,590
And, as Henry said, in the old-days you had
kind of a diaphragm.
1344
01:45:38,590 --> 01:45:45,590
Everything was in like a little balloon and
you would pressurize the outside of the balloon
1345
01:45:48,610 --> 01:45:50,369
and that would force the fuel out, but that
balloon would get eaten away.
1346
01:45:50,369 --> 01:45:52,860
I mean remember that was a system that is
only used for one flight.
1347
01:45:52,860 --> 01:45:56,900
Now we have a system that has to be reusable.
1348
01:45:56,900 --> 01:46:02,489
And if you didn't want to replace those diaphragms
or balloons every flight you needed something
1349
01:46:02,489 --> 01:46:03,750
that was a different system.
1350
01:46:03,750 --> 01:46:08,880
And that is where they came up with the idea
of the screens which would have surface tension
1351
01:46:08,880 --> 01:46:12,780
so enough of the propellant would stick to
the screen.
1352
01:46:12,780 --> 01:46:19,780
And then you would get the helium on the other
side that would push it out of the screen.
1353
01:46:20,300 --> 01:46:27,300
With the OMS, of course, once you got the
system started then you're producing an acceleration.
1354
01:46:29,580 --> 01:46:35,290
And it is always in the same direction so
that the OMS tanks are designed so that they
1355
01:46:35,290 --> 01:46:40,699
only have to feed enough propellant through
the screening system to get the engine started.
1356
01:46:40,699 --> 01:46:45,690
And then everything, I won't call it gravity-fed,
but is fed by the acceleration.
1357
01:46:45,690 --> 01:46:48,760
When both engines are burning, it is about
a tenth of a G.
1358
01:46:48,760 --> 01:46:53,119
But the RCS, that can push you in any direction.
1359
01:46:53,119 --> 01:46:59,739
And so you have to have a system which will
continuously feed, no matter which direction
1360
01:46:59,739 --> 01:47:01,820
your acceleration vector is.
1361
01:47:01,820 --> 01:47:04,429
It is a really complex and cleaver system.
1362
01:47:04,429 --> 01:47:09,170
And the design is based strictly on surface
tension.
1363
01:47:09,170 --> 01:47:11,679
Why are there so many RCS engines?
1364
01:47:11,679 --> 01:47:18,679
For example, in the nose, there are 16.
1365
01:47:19,510 --> 01:47:22,730
Is that for redundancy?
1366
01:47:22,730 --> 01:47:25,889
Part of it is for redundancy and part of it
is to make sure that you've got one to cover
1367
01:47:25,889 --> 01:47:28,940
every direction.
1368
01:47:28,940 --> 01:47:31,909
I guess we've got six going down in front.
1369
01:47:31,909 --> 01:47:37,050
Now, we need two of those for certain maneuvers.
1370
01:47:37,050 --> 01:47:41,429
So you can lose four of them.
1371
01:47:41,429 --> 01:47:46,010
And we have four going out.
1372
01:47:46,010 --> 01:47:49,030
You can lose one on either side.
1373
01:47:49,030 --> 01:47:53,900
And remember you need a couple pair.
1374
01:47:53,900 --> 01:47:59,119
You would like to be able to do a pure rotation.
1375
01:47:59,119 --> 01:48:04,929
If you just fire one engine in the aft you're
going to get a rotation, but you will also
1376
01:48:04,929 --> 01:48:05,310
get a translation.
1377
01:48:05,310 --> 01:48:07,570
So, you need a couple pairs.
1378
01:48:07,570 --> 01:48:10,320
And then for redundancy we have three sets.
1379
01:48:10,320 --> 01:48:16,400
If you add up the x-axis, the y-axis, the
z-axis, you've got to be able to translate
1380
01:48:16,400 --> 01:48:23,400
in three axies, you've got to be able to rotate
about three axies, and then you need dual
1381
01:48:23,650 --> 01:48:26,230
redundancy for each of that axis.
1382
01:48:26,230 --> 01:48:30,659
You add it up and you end up with 38 primary
jets.
1383
01:48:30,659 --> 01:48:32,389
And then, on top of that, those are 850 pound
jets.
1384
01:48:32,389 --> 01:48:35,040
They use a lot of propellant.
1385
01:48:35,040 --> 01:48:40,199
When you are in orbit generally and all you
worry about is your attitude and you're not
1386
01:48:40,199 --> 01:48:46,070
doing a propulsive burn for rendezvous or
anything, we shut down the primary RCS system
1387
01:48:46,070 --> 01:48:52,639
and we just use six little 25 pound Vernier
thrusters, all of which are pointed down.
1388
01:48:52,639 --> 01:48:59,639
When you use those for attitude control they
do give you a little bit of propulsive impulse
1389
01:49:02,150 --> 01:49:03,080
as well.
1390
01:49:03,080 --> 01:49:10,080
But it is a small enough thrust that it doesn't
change your orbit by very much.
1391
01:49:10,659 --> 01:49:17,659
Let me tell you another story about the expulsion
devices on the Shuttle.
1392
01:49:22,690 --> 01:49:26,670
Back in my young days, I grew up in the country,
and we had a Ford tractor.
1393
01:49:26,670 --> 01:49:32,060
The Ford tractor had a screen in the fuel
tank and it stood up about that tall.
1394
01:49:32,060 --> 01:49:33,599
And it had a little stand pipe in there.
1395
01:49:33,599 --> 01:49:39,900
And the valve was such that when you got down
you could set the valve one way and it would
1396
01:49:39,900 --> 01:49:41,770
leave about a gallon of fuel in the tank.
1397
01:49:41,770 --> 01:49:45,650
You turn it the other way at the end and it
would use that gallon of fuel out, kind of
1398
01:49:45,650 --> 01:49:49,199
like a gas gauge on the early Volkswagen.
1399
01:49:49,199 --> 01:49:56,130
Well, what happened is that I had that out
one day and it had a tenth of an inch diameter
1400
01:49:56,130 --> 01:49:59,750
hole punched in that screen about halfway
up on the screen.
1401
01:49:59,750 --> 01:50:02,800
I said that screen is not doing any good if
it has a hole in it.
1402
01:50:02,800 --> 01:50:07,760
I got me a ball of solder and I stopped up
that screen.
1403
01:50:07,760 --> 01:50:13,179
You know, after that, you could have it set
where the fuel are supposed to remain in the
1404
01:50:13,179 --> 01:50:13,429
tank.
1405
01:50:13,239 --> 01:50:15,449
And when it quit it was empty.
1406
01:50:15,449 --> 01:50:17,679
You'd switch it over and it still wouldn't
run.
1407
01:50:17,679 --> 01:50:18,409
You couldn't get home.
1408
01:50:18,409 --> 01:50:20,150
You would have to walk home.
1409
01:50:20,150 --> 01:50:27,150
Well, it turned out that they had put that
hole in there as a vacuum breaker to break
1410
01:50:27,510 --> 01:50:29,330
the vacuum on it.
1411
01:50:29,330 --> 01:50:33,880
And that is the way that the Shuttle system
works.
1412
01:50:33,880 --> 01:50:38,909
The screens that we have in there, it is fine
enough so that the surface tension across
1413
01:50:38,909 --> 01:50:43,429
those small pores is strong enough so that
it will keep the air from punching through,
1414
01:50:43,429 --> 01:50:45,760
unless you put a big hole in them.
1415
01:50:45,760 --> 01:50:48,679
We had to make sure.
1416
01:50:48,679 --> 01:50:54,219
And that was another one of the things that
convinced me that we could design a screen
1417
01:50:54,219 --> 01:50:59,119
system that would work in the absence of gravity.
1418
01:50:59,119 --> 01:51:03,650
It goes back to a Ford tractor.
1419
01:51:03,650 --> 01:51:07,330
It goes all the way back to 1947 and a Ford
tractor.
1420
01:51:07,330 --> 01:51:08,119
Henry, we've come to the end.
1421
01:51:08,119 --> 01:51:08,369
Let's thank Henry.
1422
01:51:08,179 --> 01:51:08,429
[APPLAUSE]